IP-P2-SCSI-DRIV.NPL - Comprehensive Analysis¶

File: IP-P2-SCSI-DRIV.NPL

Purpose: SCSI Driver for ND-100 with NCR 5386 Controller

Table of Contents¶

Symbol Definitions
Entry Points
Main APIs/Subroutines
Interrupt Flow (SCINT)
Phase Handlers
Support Routines
Error Handling

Symbol Definitions¶

Error Conditions (Lines 17-19)¶

7SIDE = 5    % Initiator Detected Error
7SMRJ = 7    % Message Reject
7SMPE = 11   % Message Parity Error

Hardware Register Addresses (Lines 25-69)¶

Controller Registers¶

RLMAR = 00   % Read Memory Address Register bits 14-0
WLMAR = 01   % Write Memory Address Register bits 14-0
REDAT = 02   % Read Data
WRDAT = 03   % Write Data
RSTAU = 04   % Read Status
WCONT = 05   % Write Control
RHMAR = 06   % Read Memory Address Register bits 23-15
WHMAR = 07   % Write Memory Address Register bits 23-15

NCR 5386 Registers¶

RNDAT = 40   % Read NCR Data Register
WNDAT = 41   % Write NCR Data Register
RNCOM = 42   % Read NCR Command Register
WNCOM = 43   % Write NCR Command Register
RNCNT = 44   % Read NCR Control Register
WNCNT = 45   % Write NCR Control Register
RDESI = 46   % Read Destination ID Register
WDESI = 47   % Write Destination ID Register
RAUXS = 50   % Read Auxiliary Status
WAUXS = 51   % Write Auxiliary Status
ROIDN = 52   % Read Own ID Number
RITRG = 54   % Read Interrupt Register
RSOUI = 56   % Read Source ID
RDIST = 62   % Read Diagnostic Status
RTCM  = 70   % Read Transfer Counter Most significant
WTCM  = 71   % Write Transfer Counter Most significant
RTC2  = 72   % Read Transfer Counter 2nd byte
WTC2  = 73   % Write Transfer Counter 2nd byte
RTCL  = 74   % Read Transfer Counter Least significant
WTCL  = 75   % Write Transfer Counter Least significant

Status Bits (Lines 30-32, 46)¶

CTBUS = 02   % Controller Busy
NCRIT = 11   % Interrupt from NCR
SCREQ = 15   % REQ from SCSI bus
DARGF = 07   % Data Register Full
ENDMA = 05   % Enable DMA
SLFCO = 07   % Selftest Complete NCR 5386

NCR Interrupt Register Bits (Lines 51-59)¶

ILCOM = 16   % Illegal Command
RECON = 14   % Reconnect
CONEC = 13   % Connect
DISCO = 12   % Disconnect
BUSSI = 11   % Bus Service Interrupt
FUCOM = 10   % Function Complete
PARIT = 06   % Parity Error
PAUSE = 02   % Paused
TCZRO = 01   % Transfer Count Zero

Status Flags (Lines 71-81)¶

6SFUN = 17   % Function Started
6SIDE = 16   % Send Identify
6SRST = 15   % SCSI Bus Reset
6SMSO = 12   % Message Out Pending
6SRFD = 11   % Return on Command Accepted (first disconnect)
6SDIS = 10   % Disconnect Message Received
6SCCO = 7    % Command Complete Message Received
6SMSI = 6    % Message Received
6SARB = 5    % Arbitration Phase
6SSBT = 4    % Single Byte Transfer
6SCRP = 3    % Connect/Reconnect Phase

Flag Masks (Lines 83-85)¶

CNCLR = 177000   % Mask for flags cleared on connect path
DCCLR = 136400   % Mask for flags cleared on disconnect path
NPCLR = 137000   % Mask for flags cleared on new phase

Entry Points¶

SCLLD - Main Entry Point (Lines 93-117)¶

Line: 93-117

Call Sequence:

JPL I (SCLLD
JMP BUSY
JMP ERROR
JMP FIN

Entry Parameters: - A = Function Type - X = Unit Datafield

Function Types: - Type 0-2 (Lines 93-99): Normal SCSI operation - Save control and return address to X.SUCON, X.SULRG - Clear trigger: 0 = X.SUTRG - Check NCR interface OK (NCROK) - Call INITO to initialize operation - If bus free, call SELEC to start arbitration

Type 3 (Lines 101-105): Enable Timer
- Save control and return address
- Set initial status: "0" BONE 6SFUN = X.SUTHS
- Call ENTIM to enable timer

Type 4 (Lines 106-113): Reset Request
- Check if reset already in progress (NCROK NBIT 8SRST)
- Save registers (SCRXR, SCRLR)
- Perform reset via SCRST
- Return "already in progress" if reset active

Exit: - Line 116: GO SCWTI - Busy return

Main APIs/Subroutines¶

SCINT - Interrupt Handler (Lines 123-189)¶

Line: 123-189

Purpose: Main interrupt service routine for SCSI controller

Detailed Flow:

Step 1: Read Device Status (Line 123)¶

Line 123: T := HDEV+RSTAU; *IOXT    % Read device status
Line 124: IF X := 64/\A><0 THEN     % Check status bits

Step 2: Check Controller Busy (Lines 125-126)¶

Line 126: IF A BIT 2 GO SCWTI       % Controller busy - exit

Step 3: Check SCSI Bus Reset (Lines 126-128)¶

Line 126: IF A =: SCSSR BIT 5 THEN
Line 127:    T := SBRST; GO FAR SCDIS   % SCSI bus reset received

Step 4: Check Initiator Detected Error (Lines 129-131)¶

Line 129: IF A BIT 4 THEN
Line 130:    CALL SCIDE; A := SCSSR   % Initiator detected error

Step 5: Check NCR Interrupt (Lines 133-138)¶

Line 133: IF A =: SCSSR BIT 11 THEN        % Interrupt from NCR
Line 134:    "0"; T := HDEV+WCONT; *IOXT   % **CLEAR TO MEMORY** (disable interrupt)
Line 135:    T+"RAUXS-WCONT"; *IOXT        % Read auxiliary status
Line 136:    AD SHZ -10                     % Shift into accumulator
Line 137:    T+"RITRG-RAUXS"; *IOXT        % Read interrupt register
Line 138:    AD SHZ -10                     % Shift into accumulator
Line 139:    A := D =: SCNIS; 0 =: SCCCW   % Save new status

Step 6: Expected Interrupt Check (Lines 141-143)¶

Line 141: IF A/\177500 = SCEIM THEN     % Expected interrupt
Line 142:    CALL SCISR                   % Call interrupt service routine

Step 7: Unexpected Interrupt Handling (Lines 144-184)¶

Arbitration Timeout (Lines 145-158):

Line 144: A SHZ -10; X := BUSFL
Line 145: IF A=4 AND X><0 THEN
Line 146:    IF X := SCCSU><0 THEN
Line 147:       CALL DCTHR                % Disconnect logical thread
Line 149:    IF BUSFL BIT 6SARB THEN      % Arbitration timeout
Line 150:       MIN SCWAQ.SUTMR; X := 0   % Count retries
Line 151:       IF X><0 THEN
Line 152:          0 =: SCTST; CALL RSTMR % Reset timer
Line 153:          CALL RFWAQ              % Remove from wait queue
Line 154:          T := NESER; CALL TEROP  % Terminate operation

Arbitration Won (Lines 160-166):

Line 160: IF A=1 AND X BIT 6SARB THEN
Line 161:    CALL RFWAQ                    % Remove from arbitration queue
Line 162:    CNCLR/\X.SUTHS BONE 6SCRP     % Fetch flags, set connect phase
Line 163:    A =: BUSFL; CALL CNTHR        % Connect physical path
Line 164:    0 =: SCTST; CALL ENTIM        % Start timer
Line 165:    RBSIR =: SCNIH                % Allow bus service interrupts

Reconnect (Lines 167-169):

Line 167: IF A=20 AND X BZERO 6SARB BZERO 6SRST=0 THEN
Line 168:    X BONE 6SCRP =: BUSFL         % Indicate reconnect
Line 169:    RBSIR =: SCNIH                % Allow bus service interrupts

Selftest Finished (Lines 171-172):

Line 171: IF A=1 AND T := NCROK BIT 8SDIA THEN
Line 172:    GO FAR STFIN                  % Selftest finished

Parity Error (Lines 174-181):

Line 174: IF A=SCEIM SHZ -10 AND D BIT PARIT AND 11/\BUSFL=1 THEN
Line 175:    MIN SCNPE; 0/\0               % Count parity errors
Line 176:    IF 17/\BUSFL=7 THEN
Line 177:       CALL SCMPE                 % Message parity error
Line 179:       CALL SCIDE                 % Initiator detected error
Line 181:    CALL SCISR

Illegal Interrupt (Lines 182-184):

Line 182: ELSE
Line 183:    T := NCRER; GO FAR SCDIS      % Illegal interrupt

Step 8: Re-enable Interrupt (Line 187)¶

Line 187: 5\/SCCCW; T := HDEV+WCONT; *IOXT   % **ACTIVATE + ENABLE INTERRUPT**
Line 188: GO SCWTI                            % Exit interrupt handler

Key Cross-References: - Calls: SCIDE, SCISR, DCTHR, RSTMR, RFWAQ, TEROP, CNTHR, ENTIM, SCMPE - Branches: SCDIS, BUSFP, STFIN, SCWTI

SCTIO - Timeout Routine (Lines 195-273)¶

Line: 195-273

Purpose: Handles timeout conditions for SCSI operations

Entry Parameters: - Timer expired (TMR = 0)

Key Operations:

Direct Timeout Enable (Lines 195-210)¶

Line 195: IF NCROK BIT 8SCLR THEN
Line 196:    SCRSQ =: SCRSL; A := B =: SCRSQ    % Enable direct timeout
Line 197:    IF X := SCCSU><0 THEN
Line 198:       T := X.SUTRG; 0 =: X.SUTRG; CALL TEROP   % Disconnect current
Line 199:       0 =: SCCSU; "0" BONE 6SRST =: BUSFL      % Allow reconnect

Cleanup After Reset (Lines 203-209)¶

Line 203: DO WHILE X := X.SULINK><0
Line 205:    IF X.SUTHS BIT 6SRST THEN
Line 206:       CALL TEROP; GO FAR EXDRI    % Terminate operation

Restart Interface (Lines 211-216)¶

Line 211: IF NCROK><0 AND A BZERO 8SRST=0 THEN
Line 212:    0 =: NCROK =: SCTST; CALL RSTMR    % Restart timer
Line 213:    IF BUSFL BZERO 6SRST=0 THEN
Line 214:       CALL SELEC                      % Restart interface

Reset Return (Lines 217-225)¶

Line 217: IF SCRCO><0 AND NCROK NBIT 8SDIA AND NBIT 8SRIN THEN
Line 218:    0 =: SCRCO; X := SCRXR             % Return from bus reset
Line 219:    IF NCROK BIT 8SERR THEN
Line 220:       T := NCRST; SCRLR =: P          % Error return
Line 222:       T := 0; SCRLR+2 =: P            % OK return

Timeout Processing (Lines 226-270)¶

Reset Timeout (Lines 228-240):

Line 228: IF A BIT 8SRIN GO FAR SCRST    % Timeout on reset receive
Line 229: IF A BIT 8SERR THEN
Line 230:    IF X := SCTQP=0 THEN
Line 231:       IF X := SCWAQ><0 THEN CALL RFWAQ FI
Line 234:    IF X><0 THEN
Line 235:       SCRSQ =: SCRSL; A := B =: SCRSQ    % Direct timeout
Line 235:       T := NCRST; CALL TEROP             % Terminate operation

Arbitration Timeout (Lines 242-256):

Line 243: IF BUSFL BIT 6SARB THEN
Line 244:    MIN SCWAQ.SUTMR; X := 0      % Arbitration timeout
Line 245:    IF X><0 THEN
Line 246:       CALL RFWAQ; X =: SCCSU    % Terminate
Line 247:       IF X.SUTRG=CMTMO THEN
Line 248:          T := CMTMA             % Timeout, not abort
Line 250:          T := ASOTM             % Select timeout
Line 255:    T := ASOTM; GO FAR SCDIS     % Reset interface

Connection Timeout (Lines 258-268):

Line 258: IF X := SCTQP><0 THEN
Line 259:    IF X.SUTMR=0 THEN
Line 260:       IF SCCSU=X THEN
Line 261:          T := CNTMO; GO FAR SCDIS      % Connection timeout
Line 263:       CMTMO =: X.SUTRG                 % Operation timeout
Line 264:       CALL DITIM; ABFLG =: X.SUTHS     % Abort operation
Line 265:       177760/\X.SUCON\/2 =: X.SUCON    % New timeout
Line 266:       SCWAQ =: X.SULINK; X =: SCWAQ    % Insert in arbitration queue
Line 267:       -1 =: X.SUTMR; CALL SELEC        % Send abort

Exit: - Line 272: GO SCWTI - Return to wait

SELEC - Activate Controller (Lines 376-398)¶

Line: 376-398

Purpose: Start arbitration and selection on SCSI bus

Entry Parameters: - SCWAQ = Arbitration wait queue

Detailed Flow:

Save Registers (Line 376)¶

Line 376: TAD =: SVTAD; X =: SAVXR

Disable Interrupt (Line 377)¶

Line 377: -1 =: SCEIM                    % Disable interrupt

Check Wait Queue (Lines 378-394)¶

Line 378: IF X := SCWAQ><0 THEN
Line 379:    "0"; T := HDEV+WCONT; *IOXT        % **CLEAR TO MEMORY**
Line 380:    A BONE 6SARB =: BUSFL              % Indicate arbitration
Line 381:    X.SUDLU SHZ -14                    % SCSI ident
Line 382:    T+"WDESI-WCONT"; *IOXT             % Write destination ID
Line 383:    WATFS; T+"WTCM-WDESI"; *IOXT       % Set waiting time (transfer counter MSB)
Line 384:    AD SHZ 10; T+"WTC2-WTCM"; *IOXT    % Transfer counter byte 2
Line 385:    AD SHZ 10; T+"WTCL-WTC2"; *IOXT    % Transfer counter LSB
Line 386:    10; IF X := X.SUCON BIT 4SINA THEN 11 FI
Line 387:    T+"WNCOM-WTCL"; *IOXT              % **SELECT COMMAND TO NCR**
Line 388:    IF X := SCTST>>2 THEN
Line 389:       TMR =: X.SUTMR                  % Save current timer
Line 391:    1 =: SCTST; -5 =: TMR              % Enable select timeout
Line 393:    0 =: BUSFL                         % Bus free

Enable Interrupt (Line 395)¶

Line 395: 5; T := HDEV+WCONT; *IOXT      % **ENABLE INTERRUPT**

Restore and Exit (Lines 396-397)¶

Line 396: X := SAVXR; SVTAD
Line 397: EXIT

Commands Written to WCONT: 1. Line 379: Write 0 - Clear to memory (disable interrupt) 2. Line 395: Write 5 - Activate + enable interrupt

Cross-References: - Called by: SCLLD (line 99), SCDIS (line 289), timeout routine (lines 214, 267) - Uses: SCWAQ (wait queue), BUSFL (bus flags)

NEWPH - New Phase Handler (Lines 659-698)¶

Line: 659-698

Purpose: Handle SCSI bus phase transitions and update data pointers

Entry Parameters: - Called via interrupt vector when bus phase changes - BUSFL = Current bus flags - SCNIS = New interrupt status

Detailed Flow:

Save Old Status (Line 659)¶

Line 659: NEWPH: T := BUSFL               % Old status

Check if Old Phase Was Data (Lines 660-691)¶

Line 660: IF 36/\T=0 THEN                % Old phase was data
Line 661:    TAD =: SAVRG; K := 1
Line 662:    IF D NBIT TCZRO THEN

Read Transfer Counter (Lines 663-671)¶

Line 664:    T := HDEV+RTCL; *IOXT       % Read LSB of bytecount
Line 665:    AD SHZ -10
Line 666:    T+"RTC2-RTCL"; *IOXT        % Read byte 2 of bytecount
Line 667:    AD SHZ -10
Line 668:    T+"RTCM-RTC2"; *IOXT        % Read MSB of bytecount
Line 670:    A := 0; D := 0              % Zero bytecount (if TCZRO set)

Calculate Bytes Transferred (Lines 672-675)¶

Line 672: T := SCCB1; X := SCCB2; AD =: SCCBC    % Save old, store new bytecount
Line 673: *RADD SD CM2 DX; RADD SA CM1 ADC DT    % Get bytes transferred
Line 674: SCCDP; *RADD SX DD; RADD ST ADC DA     % Calculate new memory address
Line 675: AD =: SCCDP SHZ -1; X := A             % Expected MAR

Handle Odd Byte Transfer (Lines 676-683)¶

Line 676: IF M THEN                        % Stopped on odd byte
Line 677:    IF BUSFL BIT 0 THEN           % Odd byte to ND-100 memory
Line 678:       150; T := HDEV+WCONT; *IOXT     % Set test mode
Line 679:       T+"RLMAR-WCONT"; *IOXT          % Force last byte to memory
Line 680:       "0"; T+"WCONT-RLMAR"; *IOXT     % Clear test mode
Line 682:    D+1; X := X+C                 % Adjust expected MAR

Verify Memory Address Register (Lines 684-689)¶

Line 684: IF K THEN
Line 685:    T := HDEV+RLMAR; *IOXT        % Read least significant MAR
Line 686:    IF A><D GO MARER
Line 687:    T+"RHMAR-RLMAR"; *IOXT        % Read most significant MAR
Line 688:    IF A><D GO MARER
Line 697: MARER: T := ILMAR; GO FAR SCDIS  % MAR not as expected

Extract New Phase and Dispatch (Lines 692-695)¶

Line 692: AD SHZ 32 SHZ -15                % Get new phase (bits from interrupt status)
Line 693: X := NPCLR/\T\/A =: BUSFL        % Set new status
Line 695: GOSW DAOPH,DAIPH,COMPH,STAPH,FAR ILOPH,FAR ILIPH,FAR MSOPH,FAR MSIPH

Phase Dispatch Table: - Phase 0: DAOPH (Data Out) - Phase 1: DAIPH (Data In) - Phase 2: COMPH (Command) - Phase 3: STAPH (Status) - Phase 4: ILOPH (Illegal Out) - Phase 5: ILIPH (Illegal In) - Phase 6: MSOPH (Message Out) - Phase 7: MSIPH (Message In)

Cross-References: - Called via: RBSIR vector (line 121), BSISR vector (line 305) - Calls phase handlers based on bus phase - Updates: SCCDP (data pointer), SCCBC (byte count), BUSFL (bus flags)

Phase Handlers¶

DAOPH - Data Out Phase (Lines 706-741)¶

Line: 706-741

Purpose: Handle SCSI Data Out phase (host to target)

Entry Parameters: - X = Current device datafield (SCCSU) - SCCDP = Current data pointer - SCCBC = Current byte count

Flow:

Set Transfer Direction (Lines 706-707)¶

Line 706: DAOPH: 40 =: SCCCW; GO DATPH
Line 707: % 40 = Data Out direction code

Common Data Phase Handler (Lines 711-738)¶

Line 711: DATPH: IF X>=0 GO FAR ILLPH        % Phase illegal if no device
Line 712:        T := HDEV+WCONT; *IOXT      % Set transfer direction
Line 713:        SCCDP SHZ -1                % Memory address

Odd Byte Handling (Lines 714-728)¶

Line 714: IF M THEN                          % Memory address on odd byte
Line 715:    X BONE 6SSBT =: BUSFL; AD =: DWP; SCCBC
Line 716:    *RADD CM1 DD; RADD CM1 ADC DA   % Decrement bytecount
Line 717:    IF A BIT 17 GO BCZRO; AD =: SCCBC  % Bytecount negative
Line 718:    "0" =: SCCCW; *IOXT             % Clear to memory
Line 719:    124; T+"WNCOM-WCONT"; *IOXT     % "Transfer info, single byte" to NCR
Line 720:    IF X BIT 0 THEN                 % Data In
Line 721:       L =: D; CALL RINFO; D =: L := A    % Read byte
Line 722:       T := WP1; X := WP2; *LDATX   % Get MSB
Line 723:       A/\177400\/D; *STATX         % Store new word
Line 725:       T := WP1; X := WP2; *LDATX   % Get byte (Data Out)
Line 726:       T := HDEV+WNDAT; *IOXT       % Send
Line 728:    DWP; D+1; A := A+C; AD SHZ 1 =: SCCDP  % New memory address

Even Byte DMA Transfer (Lines 730-737)¶

Line 730: T+"WHMAR-WCONT"; *IOXT            % Write MSW of MAR
Line 731: A := D; T+"WLMAR-WHMAR"; *IOXT    % Write LSW of MAR
Line 732: SCCBC; IF A=D AND D=0 GO BCZRO    % Check bytecount
Line 733: T+"WTCM-WLMAR"; *IOXT             % MSB of transfer counter
Line 734: AD SHZ 10; T+"WTC2-WTCM"; *IOXT   % Byte 2 of transfer counter
Line 735: AD SHZ 10; T+"WTCL-WTC2"; *IOXT   % LSB of transfer counter
Line 736: 224; T+"WNCOM-WTCL"; *IOXT        % DMA MODE + TRANSFER INFO
Line 738: EXIT

Error Handling (Line 740)¶

Line 740: BCZRO: T := BCERR; GO FAR SCDIS   % Byte count error

NCR Commands: - Line 719: Command 124 - "Transfer info, single byte" - Line 736: Command 224 - "DMA mode + Transfer info"

Cross-References: - Called by: NEWPH phase dispatch (line 695) - Calls: RINFO (read info byte) - Branches: ILLPH, BCZRO, SCDIS

DAIPH - Data In Phase (Lines 710-741)¶

Line: 710-741

Purpose: Handle SCSI Data In phase (target to host)

Entry Parameters: - Same as DAOPH

Flow:

Set Transfer Direction (Lines 710-711)¶

Line 710: DAIPH: 140 =: SCCCW
Line 711: DATPH: % Common handler with DAOPH

Differences from DAOPH: - Line 710: 140 = Data In direction code (vs 40 for Data Out) - Lines 720-723: For odd byte transfers, reads from SCSI bus instead of sending - Otherwise identical flow to DAOPH

Cross-References: - Called by: NEWPH phase dispatch (line 695) - Shares code with DAOPH at line 711

COMPH - Command Phase (Lines 745-754)¶

Line: 745-754

Purpose: Handle SCSI Command phase (send command block)

Entry Parameters: - X = Current device (SCCSU) - X.SUCM1, X.SUCM2 = Command block address

Flow:

Validate Phase (Line 745)¶

Line 745: COMPH: IF X>=0 GO FAR ILLPH        % Phase not valid if no device

Setup Transfer (Lines 746-752)¶

Line 746: 40 =: SCCCW; T := HDEV+WCONT; *IOXT       % Set transfer direction
Line 747: SCCSU.SUCM1; T+"WHMAR-WCONT"; *IOXT       % Write MSW of MAR
Line 748: X.SUCM2; T+"WLMAR-WHMAR"; *IOXT           % Write LSW of MAR
Line 749: "0"; T+"WTCM-WLMAR"; *IOXT                % MSB of transfer counter
Line 750: T+"WTC2-WTCM"; *IOXT                       % Byte 2 of transfer counter
Line 751: 14; T+"WTCL-WTC2"; *IOXT                  % LSB of transfer counter (14 bytes)
Line 752: 224; T+"WNCOM-WTCL"; *IOXT                % DMA MODE + TRANSFER INFO
Line 753: EXIT

Key Details: - Command block is always 14 bytes (line 751) - Uses DMA transfer (command 224) - Memory address from device structure fields SUCM1/SUCM2

Cross-References: - Called by: NEWPH phase dispatch (line 695) - Branches: ILLPH

STAPH - Status Phase (Lines 758-762)¶

Line: 758-762

Purpose: Handle SCSI Status phase (receive status byte)

Entry Parameters: - X = Current device (SCCSU)

Flow:

Validate and Transfer (Lines 758-761)¶

Line 758: STAPH: IF X>=0 GO FAR ILLPH                % Phase not valid
Line 759:        124; T := HDEV+WNCOM; *IOXT         % "Transfer info, single byte" to NCR
Line 760:        L =: D; CALL RINFO                  % Read status byte
Line 761:        A =: SCCSU.SUSTA; D =: P            % Save status, return

Key Details: - Single byte transfer using programmed I/O - Status saved to SCCSU.SUSTA - Uses RINFO to poll for byte availability

Cross-References: - Called by: NEWPH phase dispatch (line 695) - Calls: RINFO - Branches: ILLPH

MSOPH - Message Out Phase (Lines 776-811)¶

Line: 776-811

Purpose: Handle SCSI Message Out phase (host to target)

Entry Parameters: - BUSFL = Current bus flags - CMSGO = Current message out buffer - X = Current device (SCCSU)

Flow:

Determine Message to Send (Lines 776-796)¶

Send IDENTIFY (Lines 776-786):

Line 776: MSOPH: IF T BIT 6SIDE THEN             % Send identify
Line 777:           IF SCCSU.SUCON BIT 4SRNA THEN
Line 778:              7/\X.SUDLU\/200           % "IDENTIFY" (no disconnect)
Line 780:              7/\X.SUDLU\/300           % "IDENTIFY" + "DISCONNECT ALLOWED"
Line 782:           IF T BIT 6SMSO THEN
Line 783:              X := BUSFL BZERO 6SMSO =: BUSFL    % Mark message transferred
Line 784:              A SHZ 10\/CMSGO; 0 =: CMSGO
Line 787:           X := A

Resend Last Message (Lines 788-790):

Line 788: IF 17/\T-6=0 THEN
Line 789:    X := LMSGO                           % Resend last message

Send Pending Message (Lines 791-796):

Line 791: IF T BIT 6SMSO THEN
Line 792:    BUSFL BZERO 6SMSO =: BUSFL          % Mark message transferred
Line 793:    X := CMSGO; 0 =: CMSGO
Line 795:    X := 10                              % "NO OPERATION"

Send Message (Lines 797-809)¶

Multi-byte Message (Lines 797-805):

Line 797: IF X =: LMSGO<0 THEN                   % Multi-byte message
Line 798:    40 =: SCCCW; T := HDEV+WCONT; *IOXT % Set transfer direction
Line 799:    T := X; SCPMB; *DEPO                % Store message in buffer
Line 800:    T := HDEV+WHMAR; *IOXT              % Write MSW of MAR
Line 801:    A := D; T+"WLMAR-WHMAR"; *IOXT      % Write LSW of MAR
Line 802:    "0"; T+"WTCM-WLMAR"; *IOXT          % MSB of transfer counter
Line 803:    T+"WTC2-WTCM"; *IOXT                % Byte 2 of transfer counter
Line 804:    2; T+"WTCL-WTC2"; *IOXT             % LSB of transfer counter (2 bytes)
Line 805:    224; T+"WNCOM-WTCL"; *IOXT          % DMA MODE + TRANSFER INFO

Single-byte Message (Lines 806-809):

Line 807: 124; T := HDEV+WNCOM; *IOXT            % "Transfer info, single byte"
Line 808: A := X; T+"WNDAT-WNCOM"; *IOXT         % Send message

Message Types: - IDENTIFY: 200 (octal) = 0x80 (no disconnect privilege) - IDENTIFY: 300 (octal) = 0xC0 (disconnect privilege) - NO OPERATION: 10 (octal) = 0x08

Cross-References: - Called by: NEWPH phase dispatch (line 695) - Uses: SCPMB (parameter block), LMSGO (last message out)

MSIPH - Message In Phase (Lines 819-870)¶

Line: 819-870

Purpose: Handle SCSI Message In phase (target to host)

Entry Parameters: - Called when target sends message

Flow:

Read First Message Byte (Lines 819-827)¶

Line 819: MSIPH: A := L =: "MIRET"
Line 820:        124; T := HDEV+WNCOM; *IOXT         % "Transfer Info, single byte"
Line 821:        CALL RINFO; A =: CMSGI              % Read message
Line 822:        IF A-1=0 THEN
Line 823:           EMEI1 =: SCNIH                   % Extended message
Line 825:           MSFCS =: SCNIH                   % Function complete next
Line 827:        BUSFL BONE 6SMSI =: BUSFL; GO MIRET % Return

Extended Message Handler (Lines 830-866)¶

Read Message Length (Lines 833-843):

Line 833: EMFC1: 4; T := HDEV+WNCOM; *IOXT          % "Message accepted"
Line 834:        EMEI2 =: SCNIH; EXIT               % Expected interrupt

Line 840: EMRML: 124; T := HDEV+WNCOM; *IOXT        % "Transfer info, single byte"
Line 841:        D := L; CALL RINFO; L := D         % Get message length
Line 842:        IF A =: SCEML>SCMBL GO FAR ILLPH   % Message too large
Line 843:        EMEI3 =: SCNIH; EXIT               % Expected interrupt

Read Message Bytes (Lines 849-865):

Line 849: EMFC2: 4; T := HDEV+WNCOM; *IOXT          % "Message accepted"
Line 850:        EMEI4 =: SCNIH; EXIT

Line 856: EMRMB: A := L =: "MIRET"
Line 857:        "0"; T := HDEV+WTCM; *IOXT         % MSB of transfer counter
Line 858:        T+"WTC2-WTCM"; *IOXT               % Byte 2 of transfer counter
Line 859:        SCEML; T+"WTCL-WTC2"; *IOXT        % LSB of transfer counter
Line 860:        X := 0; 24; T+"WNCOM-WTCL"; *IOXT  % Transfer info
Line 861:        DO
Line 862:           CALL RINFO; T := "SCEMB"+B; *SBYT    % Read and store byte
Line 863:           WHILE X+1<SCEML
Line 864:        OD
Line 865:        EMEI5 =: SCNIH; GO MIRET           % Function complete next

Interrupt Vectors: - EMEI1: Extended message byte 1 handler - EMEI2: After message accepted - EMEI3: After length received - EMEI4: After message accepted - EMEI5: After all bytes received

Cross-References: - Called by: NEWPH phase dispatch (line 695) - Calls: RINFO, MSGI - Related: MSGIN (line 307)

MSGIN - Message In Handling (Lines 307-369)¶

Line: 307-369

Purpose: Process received SCSI messages

Entry Parameters: - CMSGI = Received message byte - X = Current device (SCCSU)

Flow:

Handle Reconnect (Lines 313-327)¶

Line 313: MSGI:  IF X := SCCSU=0 THEN              % No current device
Line 314:           IF CMSGI BIT 7 THEN            % IDENTIFY message
Line 315:              AD SHZ 15 SHZ -35           % Extract LUN
Line 316:              T := HDEV+RSOUI; *IOXT      % Read bus device number
Line 317:              X := 7/\A := SCDVD(X)
Line 318:              IF X><0 AND D<X.SDNLU THEN
Line 319:                 SULEN; *RMPY SD DA
Line 320:                 X+D+"SDLEN"; T := X.SUTHS
Line 321:                 CNCLR/\T+7 =: BUSFL      % Restore flags
Line 322:                 IF T BIT 6SDIS GO FAR CNTHR   % Connect thread
Line 323:                 GO FAR SCABO                   % Abort

Process Message (Lines 330-366)¶

Message Dispatch (Line 332):

Line 332: GOSW MSG0,MSG1,MSG2,MSG3,MSG4,MSGR,MSGR,MSG7

Message Handlers:

MSG0 - Command Complete (Lines 334-335):

Line 334: MSG0: BUSFL BONE 6SCCO =: BUSFL         % Set command complete flag
Line 335:       EXIT

MSG1 - Extended Message (Lines 340-349):

Line 340: MSG1: IF SCEM1=2400 THEN                % Modify data pointer
Line 343:       IF A=2261 THEN                    % Synchronous transfer request
Line 346:       IF A=1002 THEN                    % Extended identify
Line 349:       GO FAR MSGR                        % Message reject

MSG2 - Save Data Pointer (Lines 337-338):

Line 337: MSG2: SCCDP =: X.SUSDP; SCCBC =: X.SUSBC  % Save data pointer
Line 338:       EXIT

MSG3 - Restore Pointers (Lines 352-353):

Line 352: MSG3: X.SUSDP =: SCCDP; X.SUSBC =: SCCBC  % Restore pointers
Line 353:       EXIT

MSG4 - Disconnect (Lines 355-356):

Line 355: MSG4: BUSFL BONE 6SDIS =: BUSFL          % Set disconnect flag
Line 356:       EXIT

MSG7 - Message Reject (Lines 358-365):

Line 358: MSG7: IF LMSGO/\377=5 OR =11 THEN        % Parity/IDE error message rejected
Line 359:          T := TRANE; GO FAR SCABO        % Send "ABORT"
Line 361:       IF A=14 THEN
Line 362:          T := FNIPL; GO FAR SCABO        % Not implemented
Line 364:          T := SPCER; GO FAR SCABO        % Illegal

MSGR - Message Reject (Line 368):

Line 368: MSGR:  GO FAR SCMRJ                      % Return "MESSAGE REJECT"

Accept Message (Lines 309-310)¶

Line 309: 4; T := HDEV+WNCOM; *IOXT               % "Message Accepted" to NCR
Line 310: BSISR =: SCNIH; GO HOME2                % Allow bus service interrupts

SCSI Messages: - 0 = Command Complete - 1 = Extended Message - 2 = Save Data Pointer - 3 = Restore Pointers - 4 = Disconnect - 7 = Message Reject

Cross-References: - Called by: MSIPH (line 821) - Calls: CNTHR, SCMRJ, SCABO - Branches: SCDIS

Support Routines¶

INITO - Initialize Operation (Lines 414-430)¶

Line: 414-430

Purpose: Initialize SCSI operation parameters

Entry Parameters: - X = Unit datafield - X.SUCON = Control word

Flow:

Determine Operation Type (Lines 414-424)¶

Line 414: INITO: IF X.SUCON =: D SHZ -10=0 THEN
Line 415:           INOPR                          % Normal operation
Line 416:           IF D BIT 4SRCA THEN
Line 417:              A BONE 6SRFD                % Return on command accepted
Line 420:        IF A-1=0 THEN
Line 421:           INABO                          % Abort
Line 423:           INBDR                          % Bus device reset

Operation Constants:

Line 410: INOPR := 0; * *-1/1@6SFUN+^; *-1/1@6SIDE+^    % Flags: 6SFUN, 6SIDE
Line 411: INABO := 6; * *-1/1@6SMSO+^                    % Abort: flag 6SMSO
Line 412: INBDR := 14; * *-1/1@6SMSO+^                   % Bus Device Reset: flag 6SMSO

Setup Operation (Lines 425-429)¶

Line 425: A =: X.SUTHS; -1 =: X.SUSTA              % Initial status
Line 426: X.SUIDP =: X.SUSDP; X.SUIBC =: X.SUSBC   % Initial pointers
Line 427: -2 =: X.SUTMR; "SCWAQ-SULINK"+B; T := X  % Insert in arbitration queue
Line 428: DO A =: X; WHILE X.SULINK><0 OD          % Find end of queue
Line 429: T =: X.SULINK                            % Link into queue
Line 430: EXIT

Cross-References: - Called by: SCLLD (line 98) - Sets up: SUTHS (status), SUSTA (status byte), SUSDP (data pointer), SUSBC (byte count)

CNTHR - Connect Physical Path (Lines 434-441)¶

Line: 434-441

Purpose: Connect the physical SCSI path to a logical unit

Entry Parameters: - X = Unit datafield - BUSFL = Bus flags

Flow:

Line 434: CNTHR: X =: SCCSU                        % Indicate path connected
Line 435:        IF X.SUTHS BIT 6SMSO THEN
Line 436:           A/\377 =: CMSGO                % Restore message
Line 437:           3; T := HDEV+WNCOM; *IOXT      % "Set ATN" to NCR
Line 439:        X.SUSDP =: SCCDP; X.SUSBC =: SCCBC    % Restore pointers
Line 440:        EXIT

Key Operations: - Sets SCCSU to current device - If message pending (6SMSO), restore message buffer and set ATN - Restore saved data pointers

NCR Command: - Line 437: Command 3 - "Set ATN" (Attention)

Cross-References: - Called by: SCINT (line 163), MSGIN (line 322) - Updates: SCCSU, CMSGO, SCCDP, SCCBC

DCTHR - Disconnect Physical Path (Lines 446-459)¶

Line: 446-459

Purpose: Disconnect the physical SCSI path from logical unit

Entry Parameters: - X = Unit datafield (SCCSU) - BUSFL = Bus flags

Flow:

Check Disconnect Conditions (Lines 447-457)¶

Line 447: DCTHR: A := L =: "HOME4"                 % Return address
Line 447:        IF T := X.SUTRG=0 AND BUSFL BIT 6SDIS THEN

Return on First Disconnect (Lines 448-454)¶

Line 448: IF A BIT 6SRFD THEN
Line 449:    A/\DCCLR\/CMSGO =: X.SUTHS            % Save thread status
Line 450:    T := -1                               % Intermediate return
Line 452:    A/\DCCLR\/CMSGO =: X.SUTHS            % Save thread status
Line 453:    X := 0                                % No return

Terminate on Error (Lines 456-457)¶

Line 456: CALL TEROP                               % Terminate (T=status)

Clear and Return (Line 458)¶

Line 458: 0 =: SCCSU; GO HOME4                     % Return

Flag Mask: - Line 84: DCCLR = 136400 - Flags cleared on disconnect

Cross-References: - Called by: SCINT (line 147) - Calls: TEROP - Clears: SCCSU

RSTMR - Restart Logical Unit Timer (Lines 465-477)¶

Line: 465-477

Purpose: Restart the timer for logical unit operations

Entry Parameters: - SCTST = Timer state - SCTQP = Timer queue pointer

Flow:

Line 465: RSTMR: IF SCTST=0 THEN                   % Timer not locked
Line 466:           IF X =: SAVRX := SCTQP><0 THEN % Queue not empty
Line 467:              IF X.SUTMR =: TMR><0 THEN   % New time value
Line 468:                 0 =: X.SUTMR; X =: SCTST % Indicate timer running
Line 470:                 SCRSQ =: SCRSL; A := B =: SCRSQ  % Direct timeout
Line 473:              0 =: TMR                    % Disable timer
Line 475:           X := SAVRX
Line 477:        EXIT

Key Operations: - If timer state is 0 (not locked), check timer queue - If queue has entry with timer value, start timer - Otherwise set direct timeout or disable timer

Cross-References: - Called by: Multiple locations (lines 152, 212, 269, 498, 544, 557) - Updates: TMR, SCTST

ENTIM - Enable Logical Unit Timer (Lines 486-500)¶

Line: 486-500

Purpose: Enable timer for logical unit and insert into timer queue

Entry Parameters: - L = Logical unit datafield - L.SUCON = Control word with timeout value - L.SUTMR = Timer value

Flow:

Save Registers (Line 486)¶

Line 486: ENTIM: TAD =: TITAD; X := :L =: "HOME5"

Save Current Timer (Lines 487-489)¶

Line 487: IF X := SCTST>>2 THEN
Line 488:    TMR =: X.SUTMR; 0 =: SCTST            % Save current timer

Calculate Timeout (Line 490)¶

Line 490: 17/\L.SUCON\/SHTIN; T := -1; *EXR SA    % Calculate max time

Insert in Timer Queue (Lines 491-497)¶

Line 491: D := B; X := "SCTQP-SULINK"+B
Line 492: DO
Line 493:    WHILE X =: B := X.SULINK><0 AND X.SUTMR>=T
Line 494:    T-A                                   % Subtract time
Line 495: OD
Line 496: IF X><0 THEN A-T =: X.SUTMR FI          % Update next element
Line 497: SULINK =: L.SULINK; X =: SULINK; B := D % Link into timer queue
Line 498: T =: X.SUTMR; CALL RSTMR                % Reset timer

Restore and Return (Line 499)¶

Line 499: TITAD; GO HOME5

Cross-References: - Called by: SCLLD (line 104), SCINT (line 164) - Calls: RSTMR - Updates: Timer queue (SCTQP)

DITIM - Disable Logical Unit Timer (Lines 541-560)¶

Line: 541-560

Purpose: Remove logical unit from timer queue

Entry Parameters: - L = Logical unit datafield

Flow:

Save Registers (Line 541)¶

Line 541: DITIM: TAD =: TITAD; X =: SAVX := :L =: "HOME5"

Check Timer Queue (Lines 542-558)¶

Line 542: IF X := SCTQP><0 THEN
Line 543:    IF X := SCTST>>2 THEN
Line 544:       TMR =: X.SUTMR; 0 =: SCTST         % Save timer
Line 546:    X := "SCTQP-SULINK"+B
Line 547:    DO
Line 548:       X =: D
Line 549:       WHILE X := X.SULINK><L AND X><0
Line 550:    OD
Line 551:    IF X=L THEN                           % Found in queue
Line 552:       IF T := X.SULINK =: D.SULINK><0 THEN
Line 553:          0 =: L.SULINK
Line 554:          X.SUTMR+T.SUTMR =: X.SUTMR     % Add time to next
Line 557:    CALL RSTMR

Restore and Return (Line 559)¶

Line 559: X := SAVX; TITAD; GO HOME5

Cross-References: - Called by: Timer routine (line 264) - Calls: RSTMR - Entry point for TEROP (line 541)

TEROP - Terminate Operation (Lines 508-537)¶

Line: 508-537

Purpose: Terminate SCSI operation with status

Entry Parameters: - X = Unit datafield - T = Status code - BUSFL = Bus flags

Flow:

Check Operation Status (Lines 508-533)¶

Line 508: TEROP: IF X.SUTRG=0 THEN                 % No trigger error
Line 509:           IF SCCSU=X THEN                % Currently connected
Line 510:              SCCDP =: X.SUSDP; SCCBC =: X.SUSBC  % Save data pointers
Line 511:              IF BUSFL NBIT 6SMSO THEN    % No message out pending
Line 512:                 IF A BIT 6SCCO THEN      % Command complete
Line 513:                    IF X.SUSTA<0 THEN
Line 514:                       T := NOSST         % No status received
Line 516:                       T := 0             % Command complete
Line 519:                 IF X.SUCON SHZ -10=0 AND T=0 THEN
Line 520:                    T := UNDIS           % Unexpected disconnect
Line 523:              IF T=0 THEN
Line 524:                 IF CMSGO=5 OR =11 THEN
Line 525:                    T := TRANE           % Parity error
Line 527:                    T := MNIBT           % Message not implemented
Line 531:           IF X.SUCON SHZ -10-3=0 AND CMTMO=T THEN
Line 532:              T := 0                      % Timer finished
Line 535:           A =: T                         % Error in operation
Line 537:        0 =: X.SUTHS                      % Indicate free

Status Codes: - 0 = Success - NOSST = No status received - UNDIS = Unexpected disconnect - TRANE = Parity error - MNIBT = Message not implemented

Continues into DITIM (line 541) to disable timer

Cross-References: - Called by: Multiple locations (lines 154, 198, 206, 223, 235, 456) - Falls through to: DITIM - Updates: X.SUSDP, X.SUSBC, X.SUTHS

RFWAQ - Remove From Wait for Arbitration Queue (Lines 401-404)¶

Line: 401-404

Purpose: Remove unit from arbitration wait queue

Entry Parameters: - SCWAQ = Arbitration wait queue head

Flow:

Line 401: RFWAQ: IF X := SCWAQ><0 THEN
Line 402:           X.SULINK =: SCWAQ; 0 =: X.SULINK
Line 404:        EXIT

Key Operations: - Remove head of queue - Clear link in removed element

Cross-References: - Called by: SCINT (lines 153, 161, 246), timeout routine (line 231) - Updates: SCWAQ

RINFO - Read Information Byte from SCSI Bus (Lines 877-886)¶

Line: 877-886

Purpose: Poll NCR data register for byte availability

Entry Parameters: - None

Exit Parameters: - A = Byte read from SCSI bus

Flow:

Line 877: RINFO: T := HDEV+RAUXS; -2000 =: RDCNT
Line 878:        FOR RDCNT DO
Line 879:           *IOXT                          % Read auxiliary status
Line 880:           IF A BIT DARGF THEN            % Data register full
Line 881:              T+"RNDAT-RAUXS"; *IOXT      % Read NCR data register
Line 882:              EXIT
Line 884:        OD
Line 885:        GO FAR SCINT                      % Check for interrupt (timeout)

Key Details: - Polls up to 2000 times (line 877) - Checks DARGF bit in auxiliary status (line 880) - If timeout, jumps to interrupt handler (line 885)

Cross-References: - Called by: STAPH (line 760), MSIPH (line 821), EMRML (line 841), EMRMB (line 862) - May branch to: SCINT

SCRST - Start Reset Sequence on SCSI Bus (Lines 568-621)¶

Line: 568-621

Purpose: Reset SCSI bus and NCR controller

Entry Parameters: - NCROK = NCR status flags - SCSSR = SCSI status register

Flow:

Check if Already Resetting (Line 568)¶

Line 568: SCRST: IF NCROK=0 THEN                   % Not already resetting

Save Current Timer (Line 569)¶

Line 569: IF X := SCTST>>2 THEN TMR =: X.SUTMR FI  % Save current timer

Determine Reset Type (Lines 570-574)¶

Line 570: IF SCSSR BIT 5 THEN
Line 571:    NCROK BONE 8SRIN =: NCROK; T := SBRST  % Receiving reset
Line 573:    T := LIRST                             % Local reset

Mark Current Operation (Lines 575-581)¶

Line 575: IF X := SCCSU><0 THEN
Line 576:    IF X.SUTRG=0 THEN T =: X.SUTRG FI      % Set status
Line 577:    BUSFL BONE 6SRST =: BUSFL              % Indicate reset started
Line 578:    NCROK BONE 8SCLR =: NCROK              % Recovery necessary
Line 580:    "0" BONE 6SRST =: BUSFL                % Indicate reset started

Mark All Active Operations (Lines 582-590)¶

Line 582: X := "SCTQP-SULINK"+B
Line 583: DO
Line 584:    WHILE X := X.SULINK><0                 % For all active operations
Line 585:    IF X.SUCON NBIT 4SRST AND X.SUTHS BIT 6SDIS THEN
Line 586:       A BONE 6SRST =: X.SUTHS             % Indicate reset
Line 587:       IF X.SUTRG=0 THEN T =: X.SUTRG FI   % Set status
Line 588:       NCROK BONE 8SCLR =: NCROK           % Recovery necessary
Line 590: OD

Clear Flags (Lines 592-593)¶

Line 592: NCROK/\CLMSK =: NCROK
Line 594: NCROK BONE 8SRST =: NCROK                 % Indicate reset started

Flag Mask:

Line 565: CLMSK := 0; * *-1/1@8SRIN+^; *-1/1@8SDIA+^; *-1/1@8STMR+^
Line 566:           * *-1/1@8SERR+^; *-1/177777-^

Lock Interface (Line 595)¶

Line 595: -1 =: SCEIM; 2 =: SCTST                   % Lock interface

Reset NCR Controller (Lines 596-604)¶

Line 596: "0"; T := HDEV+WNCOM; *IOXT               % Disconnect to NCR
Line 597: 20; T+"WCONT-WNCOM"; *IOXT                % Clear controller
Line 598: T+"RSTAU-WCONT"; *IOXT                    % Read status
Line 599: IF A BIT 5 THEN
Line 600:    NCROK BONE 8SRIN =: NCROK; -1 =: TMR   % Receiving RST
Line 602:    2000; T+"WCONT-RSTAU"; *IOXT           % Set reset on SCSI bus
Line 603:    -10000 =: TMR; FOR TMR DO OD           % Leave "RST" on for 250 us
Line 604:    "0"; *IOXT                             % Clear reset

Start NCR Diagnostics (Lines 605-618)¶

Line 605: T+"RDIST-WCONT"                           % Read diagnostic status
Line 606: FOR X := -1000 DO
Line 607:    *IOXT
Line 608:    WHILE A NBIT 7                         % Wait for ready
Line 609: OD
Line 610: IF A=200 THEN                             % Selfcheck OK
Line 611:    NCROK BONE 8SDIA =: NCROK
Line 612:    13; T := HDEV+WNCOM; *IOXT             % Start diagnostic
Line 613:    376; T+"WNDAT-WNCOM"; *IOXT            % Write data register
Line 614:    5; T+"WCONT-WNDAT"; *IOXT              % Enable interrupt
Line 615:    -2 =: TMR                              % Diagnostic timer
Line 617:    100000 =: NCROK                        % Error in interface

Timing: - Line 603: Reset held for 250 microseconds (10000 loops) - Line 606: Wait up to 1000 loops for diagnostic ready

NCR Commands: - Line 596: Command 0 - "Disconnect" - Line 597: Command 20 (octal) - Clear controller (write to WCONT) - Line 602: Value 2000 (octal) - Set RST on SCSI bus - Line 612: Command 13 (octal) - Start diagnostic - Line 613: Value 376 (octal) - Diagnostic test pattern

Cross-References: - Called by: SCLLD (line 109), SCDIS (line 286), timeout routine (line 228) - Branches to: SCTIO (line 620)

STFIN - Terminate Reset on SCSI Bus (Lines 625-653)¶

Line: 625-653

Purpose: Complete reset sequence after diagnostics

Entry Parameters: - NCROK = NCR status flags - TMR = Timer value

Flow:

Check Diagnostics (Lines 625-645)¶

Line 625: STFIN: IF NCROK BIT 8SDIA THEN            % Diagnostics running
Line 626:           A BZERO 8SDIA =: NCROK          % Diagnostics finished
Line 627:           IF TMR><0 AND D BIT DARGF THEN  % Timer OK and data ready
Line 628:              T := HDEV+RNDAT; *IOXT       % Read data register
Line 629:              16; T+"WNCNT-RNDAT"; *IOXT   % Set NCR control
Line 630:              IF A NBIT 1 THEN
Line 631:                 5; T+"WCONT-WNCNT"; *IOXT % Enable interrupt
Line 633:              0 =: TMR
Line 634:              IF T := NCROK BIT 8SPWF THEN
Line 635:                 T BZERO 8SPWF; X := SLTMR % Long timer (power lost)
Line 637:                 X := SRTMR                % Reset timer
Line 639:              IF SCRCO NBIT 0 THEN
Line 640:                 X =: TMR; T BONE 8STMR    % Allow device settle time
Line 642:              T =: NCROK
Line 644:              0 =: TMR; 100000 =: NCROK    % Error in interface

Reset Timer Expired (Lines 647-651)¶

Line 647: IF A BIT 8STMR THEN
Line 648:    A BZERO 8STMR =: NCROK; 0 =: TMR       % Reset finished
Line 650:    0 =: TMR; 100000 =: NCROK              % Error in interface

Return to Timeout Routine (Line 652)¶

Line 652: GO FAR SCTIO

NCR Setup: - Line 629: Write 16 (octal) to control register - Sets up NCR operating mode

Cross-References: - Called by: SCINT (line 172), timeout routine (line 239) - Branches to: SCTIO

Error Handling¶

SCDIS - Fatal Error: Reset SCSI Bus (Lines 278-287)¶

Line: 278-287

Purpose: Handle fatal errors by resetting SCSI bus

Entry Parameters: - T = Error code - X = Current device (SCCSU)

Flow:

Save Error Status (Lines 278-285)¶

Line 278: SCDIS: IF X := SCCSU><0 THEN
Line 279:           IF X.SUTRG=0 THEN T =: X.SUTRG FI  % Set error code
Line 281:        BUSFL =: SEST1                        % Save status
Line 282:        SCSSR =: SEST2
Line 283:        SCNIS =: SEST3
Line 284:        CMSGI =: SEST4
Line 285:        CMSGO =: SEST5
Line 286:        T =: SCLRE; GO FAR SCRST              % Reset SCSI bus

Saved Status Variables (Lines 89-91):

Line 89: DISP -32
Line 90:    INTEGER SEST1, SEST2, SEST3, SEST4, SEST5
Line 91: PSID

Cross-References: - Called from: Multiple error paths (lines 96, 127, 183, 255, 261, 326, 697, 740, 766, 771, 870) - Branches to: SCRST - Saves to: SEST1-SEST5, SCLRE

BUSFP - Bus Free Phase (Lines 289-290)¶

Line: 289-290

Purpose: Handle bus free phase, check for pending arbitration

Flow:

Line 289: BUSFP: CALL SELEC                          % Check arbitration queue
Line 290: % EXIT DRIVER...

Cross-References: - Called by: SCINT (line 157) - Calls: SELEC - Falls through to: EXDRI

EXDRI - Exit Driver (Lines 292-300)¶

Line: 292-300

Purpose: Return to caller with status

Entry Parameters: - X = LUN datafield or 0 - T = Status code

Flow:

Check Return Address (Line 292)¶

Line 292: EXDRI: IF X=0 GO SCWTI; X.SULRG            % No return

Normal Return (Lines 293-294)¶

Line 293: IF T=0 THEN A+2 =: P FI                   % Normal return (JMP FIN)

Intermediate Return (Lines 294-296)¶

Line 294: IF T<0 THEN
Line 295:    A+1                                     % Intermediate return (JMP ERROR)

Error Return (Lines 297-298)¶

Line 297: ELSE
Line 298:    MIN ERCNT; 0/\0                         % Error return (JMP BUSY)

Set Return Address (Line 299)¶

Line 299: A =: P

Return Convention: - T = 0: Jump to FIN (offset +2) - T < 0: Jump to ERROR (offset +1) - T > 0: Jump to BUSY (offset +0)

Cross-References: - Called by: Multiple locations (lines 96, 200, 206, 223, 236, 292) - Uses: SULRG (return address)

Error Message Handlers¶

SCMRJ - Set "Message Reject" (Lines 891-892)¶

Line: 891-892

Purpose: Send MESSAGE REJECT to target

Flow:

Line 891: SCMRJ: 7SMRJ; T := SPCER; GO EMSGO         % Send message

Message Code: - 7SMRJ = 7 (octal) = MESSAGE REJECT

Cross-References: - Called by: MSGIN (line 368) - Branches to: EMSGO

SCMPE - Set "Message Parity Error" (Lines 895-896)¶

Line: 895-896

Purpose: Send MESSAGE PARITY ERROR to target

Flow:

Line 895: SCMPE: BUSFL BZERO 6SMSI =: BUSFL          % Throw away message
Line 896:        7SMPE; T := TRANE; GO EMSGO

Message Code: - 7SMPE = 11 (octal) = MESSAGE PARITY ERROR

Cross-References: - Called by: SCINT (line 177) - Branches to: EMSGO

SCIDE - Set "Initiator Detected Error" (Lines 900-901)¶

Line: 900-901

Purpose: Send INITIATOR DETECTED ERROR to target

Flow:

Line 900: SCIDE: IF BUSFL BIT 6SMSO AND CMSGO=7SIDE THEN EXIT FI
Line 901:        7SIDE; T := TRANE; GO EMSGO

Message Code: - 7SIDE = 5 (octal) = INITIATOR DETECTED ERROR

Cross-References: - Called by: SCINT (lines 130, 179) - Branches to: EMSGO

SCABO - Abort Operation (Lines 907-917)¶

Line: 907-917

Purpose: Send ABORT message to target

Entry Parameters: - T = Error code - X = Current device (SCCSU)

Flow:

Line 907: SCABO: IF X := SCCSU><0 THEN
Line 908:           IF X.SUTRG=0 THEN T =: X.SUTRG FI  % Set error message
Line 910:        "6"                                    % ABORT message

Message Code: - "6" (octal) = ABORT

Falls through to EMSGO (line 915)

Cross-References: - Called by: MSGIN (lines 323, 359, 362, 364) - Falls through to: EMSGO

EMSGO - Indicate Message Ready (Lines 903-917)¶

Line: 903-917

Purpose: Set message out pending and assert ATN

Entry Parameters: - A = Message byte

Flow:

Line 903: EMSGO: IF X := BUSFL BIT 6SMSO THEN        % Message already pending
Line 915:        A =: CMSGO; T := BUSFL BONE 6SMSO =: BUSFL  % Send message
Line 916:        3; T := HDEV+WNCOM; *IOXT           % "Set ATN" to NCR
Line 917:        EXIT

NCR Command: - Line 916: Command 3 - "Set ATN"

Cross-References: - Called by: SCMRJ, SCMPE, SCIDE, SCABO - Updates: CMSGO, BUSFL

Interrupt Flow Summary¶

Complete Interrupt Flow with Line Numbers¶

Interrupt Entry (Line 123)
- Read device status from RSTAU
Initial Status Checks (Lines 124-132)
- Check controller busy (line 126)
- Check SCSI bus reset (lines 126-128)
- Check initiator detected error (lines 129-131)
NCR Interrupt Processing (Lines 133-187)
- Line 133: Check NCRIT bit (interrupt from NCR)
- Line 134: Write 0 to WCONT (disable interrupt/clear to memory)
- Line 135: Read auxiliary status (RAUXS)
- Line 137: Read interrupt register (RITRG)
- Line 139: Save status to SCNIS
Expected Interrupt (Lines 141-143)
- Check if interrupt matches expected
- Call SCISR (interrupt service routine)
Unexpected Interrupt Handling (Lines 144-184)
- Arbitration timeout (lines 145-158)
- Arbitration won (lines 160-166)
- Reconnect (lines 167-169)
- Selftest finished (lines 171-172)
- Parity error (lines 174-181)
- Illegal interrupt (lines 182-184)
Re-enable Interrupt (Line 187)
- Line 187: Write 5 to WCONT (activate + enable interrupt)
Exit (Line 188)
- Return to wait state

Key Register Operations in SCINT¶

Line 123: Read RSTAU        -> Device status
Line 134: Write 0 to WCONT  -> Disable interrupt
Line 135: Read RAUXS        -> Auxiliary status
Line 137: Read RITRG        -> Interrupt register
Line 187: Write 5 to WCONT  -> Enable interrupt

Interrupt Vectors¶

Bus Service Interrupt Handlers: - RBSIR (Line 121): Points to NEWPH initially - BSISR (Line 305): Used by MSGIN for phase changes

Extended Message Handlers: - EMEI1 (Line 815): Extended message byte 1 - EMEI2 (Line 831): After message accepted - EMEI3 (Line 838): After length received - EMEI4 (Line 847): After message accepted - EMEI5 (Line 854): After all bytes received

Function Complete Handlers: - MSFCS (Line 816): Standard message handler - EMFC1 (Line 815): Extended message function complete - EMFC2 (Line 847): Extended message function complete

Cross-Reference Summary¶

Major Call Chains¶

Initialization:

SCLLD -> INITO -> SELEC

Interrupt Processing:

SCINT -> SCISR -> (phase handlers)
      -> DCTHR -> TEROP -> DITIM
      -> CNTHR
      -> ENTIM -> RSTMR

Phase Changes:

NEWPH -> DAOPH/DAIPH/COMPH/STAPH/MSOPH/MSIPH
      -> MSGIN -> MSG0/MSG1/MSG2/MSG3/MSG4/MSG7

Error Handling:

(error) -> SCDIS -> SCRST -> STFIN -> SCTIO
        -> SCMRJ/SCMPE/SCIDE/SCABO -> EMSGO

Timeout:

SCTIO -> TEROP -> DITIM -> RSTMR
      -> SCRST
      -> SELEC

Summary¶

This SCSI driver implements a complete initiator-mode SCSI interface using the NCR 5386 controller. Key features:

Interrupt-driven operation with comprehensive interrupt handling
Full SCSI phase support (Data, Command, Status, Message)
Arbitration and selection with retry logic
Disconnect/reconnect support
Timer management for timeouts and retries
Error recovery including bus reset
Message handling including extended messages
DMA transfers for data and command phases
Parity error detection and recovery

The driver carefully manages hardware registers, particularly WCONT (control register), which is used to enable/disable interrupts, clear the controller, and set SCSI bus signals like RST.

Critical interrupt flow ensures: - Interrupts disabled during processing (line 134: write 0 to WCONT) - Status registers read before being cleared - Interrupts re-enabled before exit (line 187: write 5 to WCONT) - Expected interrupts handled via vector table - Unexpected interrupts analyzed and recovered

The phase handlers implement the full SCSI protocol, including: - DMA setup for bulk transfers - Programmed I/O for single-byte transfers - Proper handling of odd-byte boundaries - Message protocol support - Data pointer save/restore

File Information¶

Full Path: Source Code\Sintran L\NPL\IP-P2-SCSI-DRIV.NPL

Total Lines: 921

Date Stamp: 066562 (visible in octal at file header)

Entry Points Defined: - SCLLD (line 93) - SCINT (line 123) - SCTIO (line 195)

Key Global Variables: - NCROK: NCR controller status - BUSFL: Bus flags - SCCSU: Current device pointer - SCWAQ: Arbitration wait queue - SCTQP: Timer queue pointer - SCCDP: Current data pointer - SCCBC: Current byte count