N500DF Structure - Complete Reference¶
ND-500 Datafield Structure - Complete Documentation
Version: 1.0
Date: 2025-01-XX
Status: Complete
Source: Analysis of SINTRAN III NPL source code (5P-P2-MON60.NPL, MP-P2-N500.NPL, symbol files)
Table of Contents¶
- Overview
- Structure Definition
- Allocation and Lifecycle
- Parameter Offsets
- GND5PAR Routine
- Usage Examples
- Complete Field Reference
1. Overview¶
1.1 What is N500DF?¶
N500DF (ND-500 Datafield) is a work area structure used by SINTRAN to store parameters extracted from ND-500 monitor call messages. It acts as a local buffer in ND-100 memory where parameters from the 5MPM message buffer are copied for easier access.
Key Characteristics: - Location: ND-100 memory (not in 5MPM) - Purpose: Temporary work area for processing ND-500 monitor calls - Size: Approximately 200₈ (128₁₀) words (exact size depends on maximum parameters) - Lifetime: Allocated per-process, released after monitor call processing
1.2 Why N500DF Exists¶
The Problem:
- ND-500 writes monitor call parameters to 5MPM message buffer (shared memory)
- Accessing 5MPM requires special bank register setup (T:=5MBBANK)
- Multiple accesses to the same parameters would require repeated bank setup
- Parameters are scattered throughout the message buffer
The Solution:
- GND5PAR routine copies parameters from 5MPM message buffer to N500DF
- N500DF is in regular ND-100 memory (no bank setup needed)
- Parameters are stored at fixed offsets for easy access
- Code can access parameters directly: 5D12=:ADRZERO (no bank setup)
1.3 Relationship to Message Buffer¶
flowchart LR
A[ND-500<br/>Writes Message] --> B[5MPM Message Buffer<br/>Shared Memory]
B --> C[GND5PAR Routine<br/>Extracts Parameters]
C --> D[N500DF Structure<br/>ND-100 Memory]
D --> E[SINTRAN Code<br/>Accesses Parameters]
style A fill:#e1f5ff
style B fill:#fff9c4
style C fill:#ffccbc
style D fill:#c8e6c9
style E fill:#f3e5f5Flow: 1. ND-500 writes monitor call parameters to 5MPM message buffer 2. GND5PAR reads parameters from 5MPM and stores them in N500DF 3. SINTRAN code accesses parameters from N500DF (no bank setup needed)
2. Structure Definition¶
2.1 Memory Layout¶
N500DF Structure Layout:
Offset (Oct) | Offset (Dec) | Symbol | Size | Purpose
-------------|--------------|-----------|------|--------------------------
000000 | 0 | (base) | - | N500DF base address
000001 | 1 | 5FUNCTION | 1 | Monitor call function code
000002 | 2 | (reserved)| - |
... | ... | ... | ... | Reserved area
000040 | 32 | 5D11 | 1 | Parameter 11 (MEMDEF: pointer to memory config)
000041 | 33 | 5D12 | 1 | Parameter 12 (MEMDEF: ADRZERO page number)
000042 | 34 | 5P1 | 1 | Parameter 1 (single word)
000043 | 35 | 5D21 | 1 | Parameter 21
000044 | 36 | 5D22 | 1 | Parameter 22 (MEMDEF: number of memory parts)
000045 | 37 | 5P2 | 1 | Parameter 2 (single word)
000046 | 38 | 5D31 | 1 | Parameter 31
000047 | 39 | 5D32 | 1 | Parameter 32
000050 | 40 | 5P3 | 1 | Parameter 3 (single word)
000051 | 41 | 5D41 | 1 | Parameter 41
000052 | 42 | 5D42 | 1 | Parameter 42
000053 | 43 | 5P4 | 1 | Parameter 4 (single word)
000054 | 44 | 5D51 | 1 | Parameter 51
000055 | 45 | 5D52 | 1 | Parameter 52
... | ... | ... | ... | Additional parameters
000100 | 64 | 5AP1 | 2 | Parameter 1 (double word, input)
000101 | 65 | 5DP1 | 2 | Parameter 1 (double word, output)
000102 | 66 | 5AP2 | 2 | Parameter 2 (double word, input)
000103 | 67 | 5DP2 | 2 | Parameter 2 (double word, output)
000104 | 68 | 5AP3 | 2 | Parameter 3 (double word, input)
000105 | 69 | 5DP3 | 2 | Parameter 3 (double word, output)
000106 | 70 | 5AP4 | 2 | Parameter 4 (double word, input)
000107 | 71 | 5DP4 | 2 | Parameter 4 (double word, output)
... | ... | ... | ... | Additional double-word parameters
000126 | 86 | 5ECH1 | 1 | Echo parameter 1
000130 | 88 | 5ECH2 | 1 | Echo parameter 2
000132 | 90 | 5ECH3 | 1 | Echo parameter 3
... | ... | ... | ... | Additional fields
Note: The exact size depends on the maximum number of parameters supported. Based on symbol files, the structure appears to be at least 200₈ (128₁₀) words.
2.2 Symbol Values (Verified from Symbol Files)¶
Source: SYMBOL-1-LIST.SYMB.TXT
| Symbol | Octal Value | Decimal | Hex | Offset in N500DF | Purpose |
|---|---|---|---|---|---|
| 5D11 | 000040 | 32 | 0x20 | Parameter 11 | MEMDEF: Pointer to memory config data |
| 5D12 | 000041 | 33 | 0x21 | Parameter 12 | MEMDEF: ADRZERO (base page number) |
| 5D22 | 000044 | 36 | 0x24 | Parameter 22 | MEMDEF: Number of memory parts |
| 5P1 | 000042 | 34 | 0x22 | Parameter 1 | Single-word parameter 1 |
| 5P2 | 000045 | 37 | 0x25 | Parameter 2 | Single-word parameter 2 |
| 5P3 | 000050 | 40 | 0x28 | Parameter 3 | Single-word parameter 3 |
| 5P4 | 000053 | 43 | 0x2B | Parameter 4 | Single-word parameter 4 |
| 5AP1 | 000100 | 64 | 0x40 | Parameter 1 (input) | Double-word parameter 1 (input) |
| 5DP1 | 000101 | 65 | 0x41 | Parameter 1 (output) | Double-word parameter 1 (output) |
| 5AP2 | 000102 | 66 | 0x42 | Parameter 2 (input) | Double-word parameter 2 (input) |
| 5DP2 | 000103 | 67 | 0x43 | Parameter 2 (output) | Double-word parameter 2 (output) |
| 5AP3 | 000104 | 68 | 0x44 | Parameter 3 (input) | Double-word parameter 3 (input) |
| 5DP3 | 000105 | 69 | 0x45 | Parameter 3 (output) | Double-word parameter 3 (output) |
| 5AP4 | 000106 | 70 | 0x46 | Parameter 4 (input) | Double-word parameter 4 (input) |
| 5DP4 | 000107 | 71 | 0x47 | Parameter 4 (output) | Double-word parameter 4 (output) |
| 5PPA1 | 000040 | 32 | 0x20 | Parameter pointer 1 | Pointer to parameter 1 area |
| 5PPA2 | 000042 | 34 | 0x22 | Parameter pointer 2 | Pointer to parameter 2 area |
| 5PPA3 | 000044 | 36 | 0x24 | Parameter pointer 3 | Pointer to parameter 3 area |
| 5DPA1 | 000041 | 33 | 0x21 | Parameter data 1 | Data for parameter 1 |
| 5DPA2 | 000043 | 35 | 0x23 | Parameter data 2 | Data for parameter 2 |
| 5DPA3 | 000045 | 37 | 0x25 | Parameter data 3 | Data for parameter 3 |
3. Allocation and Lifecycle¶
3.1 Allocation: 5RESWORKA Routine¶
Source: 5P-P2-MON60.NPL lines 382-396 (5RESWORKA routine)
5RESWORKA:
IF BACKGROUND=0 THEN
A:=L=:"5RLREG"
XSEMS(7)
A=:B
NYTRY: MLEV; *MCL PIE
X:=RTREF; CALL BRESERVE
IF A<0 THEN
CALL FREXQU; CALL TOWQU; CALL ANTIJAMMER
"STUPR"; *IRW MLEVB DP
MLEV; *MST PIE; MST PID
GO NYTRY
FI; MLEV; *MST PIE
"N500DF"=:B; GO 5RLREG % LINE 395: SET B=N500DF
FI; EXIT
What it does:
1. Reserves a work area using semaphore 7 (XSEMS(7))
2. Calls BRESERVE to allocate memory
3. Sets B register to point to N500DF structure ("N500DF"=:B)
4. Returns with B register pointing to allocated N500DF
Key Points: - Semaphore 7 protects N500DF allocation (mutex) - BRESERVE allocates memory from a work area pool - B register is set to N500DF base address - Allocation is per-process (RTREF-based)
3.2 Release: 5RELWORKA Routine¶
Source: 5P-P2-MON60.NPL lines 398-409 (5RELWORKA routine)
5RELWORKA:
IF BACKGROUND=0 THEN
A:=L=:"5RLREG"
XSEMS(7)
A=:B
IF X:=RTREF=RTRES THEN
*IOF
CALL BRELEASE
*ION
FI
"N500DF"=:B; GO 5RLREG % LINE 408: SET B=N500DF
FI; EXIT
What it does: 1. Checks if RTREF = RTRES (reserved RT resource) 2. Calls BRELEASE to free the work area 3. Releases semaphore 7 4. Returns with B register still pointing to N500DF (for cleanup)
3.3 Usage Pattern¶
Typical Usage:
% Entry point (e.g., CHMEMDEF)
CHMEMDEF:
A:=L=:"CHMLREG"
% ... validation ...
CALL 5RESWORKA % Allocate N500DF (B register set)
% ... process parameters ...
"5D11"+B=:D; CALL GND5PAR % Read parameters into N500DF
% ... use parameters ...
5D12=:ADRZERO % Access parameter from N500DF
% ... more processing ...
CALL 5RELWORKA % Release N500DF
EXITA
Lifecycle:
1. 5RESWORKA - Allocate N500DF (B register = N500DF base)
2. GND5PAR - Copy parameters from 5MPM to N500DF
3. Access parameters - Use offsets like 5D12, 5D22, etc.
4. 5RELWORKA - Release N500DF
4. Parameter Offsets¶
4.1 Single-Word Parameters (5D11, 5D12, 5D22, etc.)¶
MEMDEF Function Parameters:
| Parameter | Offset (Oct) | Offset (Dec) | Symbol | Purpose |
|---|---|---|---|---|
| 5D11 | 000040 | 32 | 5D11 |
Pointer to memory configuration data array |
| 5D12 | 000041 | 33 | 5D12 |
ADRZERO (base page number for 5MPM) |
| 5D22 | 000044 | 36 | 5D22 |
Number of memory parts (max 16₈) |
Access Pattern:
"N500DF"=:B % Set B register to N500DF base
"5D11"+B=:D % D = offset 5D11 (B + 40₈)
CALL GND5PAR % Read parameters from 5MPM into N500DF
5D12=:ADRZERO % Access parameter 5D12 directly
4.2 Double-Word Parameters (5AP1-5AP4, 5DP1-5DP4)¶
Double-word parameters are used for 32-bit values (addresses, counts, etc.).
| Parameter | Offset (Oct) | Offset (Dec) | Symbol | Purpose |
|---|---|---|---|---|
| 5AP1 | 000100 | 64 | 5AP1 |
Parameter 1 (input, double word) |
| 5DP1 | 000101 | 65 | 5DP1 |
Parameter 1 (output, double word) |
| 5AP2 | 000102 | 66 | 5AP2 |
Parameter 2 (input, double word) |
| 5DP2 | 000103 | 67 | 5DP2 |
Parameter 2 (output, double word) |
| 5AP3 | 000104 | 68 | 5AP3 |
Parameter 3 (input, double word) |
| 5DP3 | 000105 | 69 | 5DP3 |
Parameter 3 (output, double word) |
| 5AP4 | 000106 | 70 | 5AP4 |
Parameter 4 (input, double word) |
| 5DP4 | 000107 | 71 | 5DP4 |
Parameter 4 (output, double word) |
Access Pattern:
T:=5MBBANK % Set bank to 5MPM
"N500DF"=:B % Set B register to N500DF base
*AAX 5AP1; LDDTX % Read double-word parameter 1 (input)
AD=:PARAM1 % Store in AD register pair
*AAX 5AP2-5AP1; LDDTX % Read parameter 2 (relative offset)
AD=:PARAM2 % Store in AD register pair
Note: Double-word parameters use LDDTX (Load Double-word) instruction, which reads two consecutive words into the AD register pair.
5. GND5PAR Routine¶
5.1 Purpose¶
GND5PAR (Get ND-500 Parameters) is a routine that extracts parameters from the 5MPM message buffer and stores them in the N500DF structure.
5.2 Calling Convention¶
Source: 5P-P2-MON60.NPL lines 565, 1293
"5D11"+B=:D % D = base offset (e.g., 5D11 = 40₈)
X:=ZAREG % X = ZAREG (message buffer address)
OLDPAGE % Save current page
X+1=:B % B = message buffer address + 1
T:=3 % T = number of parameters to read
CALL GND5PAR % Read T parameters starting at offset D
Parameters:
- D register: Base offset in N500DF (e.g., "5D11" = 40₈)
- B register: Message buffer address in 5MPM (after X+1=:B)
- T register: Number of parameters to read (e.g., 3 for 5D11, 5D12, 5D22)
- X register: Message buffer base address (ZAREG)
What GND5PAR does: 1. Reads T parameters from 5MPM message buffer (starting at X+1) 2. Stores them in N500DF structure (starting at offset D) 3. Returns with parameters available in N500DF
5.3 Example: MEMDEF Function¶
Source: 5P-P2-MON60.NPL lines 565-567 (CHMEMDEF routine)
CHMEMDEF:
% ... setup code ...
"5D11"+B=:D; X:=ZAREG; OLDPAGE; X+1=:B; T:=3; CALL GND5PAR
% ^
% |
% Read 3 parameters: 5D11, 5D12, 5D22
"N500DF"=:B
IF 5D22>MXMPARTS GO CHMEEILPAR % Access 5D22 directly
A=:MPARTS
% ... process memory configuration ...
5D12=:ADRZERO % Access 5D12 directly
What happens:
1. "5D11"+B=:D - D = N500DF base + 40₈ (offset of 5D11)
2. X:=ZAREG - X = message buffer base address
3. X+1=:B - B = message buffer address + 1 (skip header?)
4. T:=3 - Read 3 parameters
5. CALL GND5PAR - Copy parameters from 5MPM to N500DF
6. 5D22=:MPARTS - Access parameter directly from N500DF
7. 5D12=:ADRZERO - Access parameter directly from N500DF
5.4 GND5PAR Implementation (Not in Source)¶
GND5PAR is likely a library routine or microcode (not found in NPL source). Based on usage patterns, it likely:
GND5PAR:
% Input: D = N500DF offset, B = message buffer address, T = count
% X = message buffer base (from ZAREG)
FOR I := 0 TO T-1 DO
% Read word from message buffer
T:=5MBBANK % Set bank to 5MPM
*AAX (B + I); LDATX % Read word at offset (B + I)
A=:TEMP
% Write word to N500DF
T:=0 % Clear bank (ND-100 memory)
X:=N500DF + D + I % Calculate N500DF offset
TEMP=:X % Store parameter
OD
EXITA
Note: This is speculation based on usage patterns. The actual implementation may differ.
6. Usage Examples¶
6.1 Example 1: MEMDEF Function (Memory Definition)¶
Source: 5P-P2-MON60.NPL lines 515-587 (CHMEMDEF routine)
CHMEMDEF:
A:=L=:"CHMLREG"
IF 5FUNCTION><MEMDEF THEN % If NOT MEMDEF (40₈)
IF ADRZERO=-1 THEN
EMDFCOM; GO CHMLREG % Error: memory not defined
FI
EXITA
FI; GO CHM1
CHM1:
% ... setup code ...
% Read parameters from 5MPM message buffer into N500DF
"5D11"+B=:D; X:=ZAREG; OLDPAGE; X+1=:B; T:=3; CALL GND5PAR
"N500DF"=:B
% Access parameters from N500DF
IF 5D22>MXMPARTS GO CHMEEILPAR % Check number of memory parts
A=:MPARTS
% Copy memory configuration data
5P3=:D; 5D22 SH 1=:X; OLDPAG; K:="0"; CALL MOVUS
% Process memory configuration...
% Set ADRZERO from parameter 5D12
5D12=:ADRZERO % LINE 587: KEY LINE!
% ... cleanup ...
CALL 5RELWORKA % Release N500DF
EXITA
Key Points:
- GND5PAR reads 3 parameters (5D11, 5D12, 5D22) from 5MPM
- 5D22 contains number of memory parts
- 5D11 contains pointer to memory configuration data
- 5D12 contains ADRZERO (base page number)
- Parameters are accessed directly: 5D12=:ADRZERO
6.2 Example 2: N500M Entry Point¶
Source: 5P-P2-MON60.NPL lines 1285-1297 (N500M routine)
N500M: CALL GET1 % Get function parameter
IF X:=5FUNCTION BZERO COMAUTO>>FUNCMAX GO FAR ILLFUNC
% ... validation ...
% Read message parameters from 5MPM buffer
T:=XPARANT
SKPLG: "5D11"+B=:D; X:=ZAREG
A:=OLDPAGE; X+1=:B; CALL GND5PAR % FETCH MON-60 PARAMETERS
"N500DF"=:B; X:=5FUNCTION; *1BANK
A:=5IFUNC(X); *2BANK % Get function handler address
A=:P % Jump to function handler
Key Points: - GND5PAR reads parameters for the current monitor call - XPARANT determines how many parameters to read - Parameters are stored in N500DF for function handler access - Function handler can access parameters directly from N500DF
6.3 Example 3: UDMA Function (Fast UDMA)¶
Source: MP-P2-N500.NPL lines 1455-1465 (N5FUD routine)
N5FUD:
%-------------------------- GET PARAMETERS
T:=5MBBANK; *LDATX X5SND % GET 500 PROC. NO
A=:N5SE
*AAX 5PPA2; LDDTX % GET BUFFER ADDRESS
AD=:DBUA; *AAX 5AP1-5PPA2; LDDTX % GET FUNCTION (parameter 1)
IF A >< 0 GO UERR; A:=D=:UFU
*AAX 5AP2-5AP1; LDDTX % GET PIO DATA (parameter 2)
A:=D=:UPIO
*AAX 5AP3-5AP2; LDDTX % GET LOG DEV (parameter 3)
IF A >< 0 GO UERR; A:=D=:UNI
*AAX 5AP4-5AP3; LDDTX % GET IPAR1 (parameter 4)
AD=:IPAR1
Key Points:
- Double-word parameters are accessed using LDDTX (Load Double-word)
- Relative offsets are used: 5AP2-5AP1, 5AP3-5AP2, etc.
- 5MBBANK must be set before accessing parameters
- Parameters are read directly from 5MPM (not from N500DF in this case)
Note: This example reads directly from 5MPM, but parameters could also be accessed from N500DF if GND5PAR was called first.
7. Complete Field Reference¶
7.1 Function Code¶
| Offset (Oct) | Offset (Dec) | Symbol | Size | Purpose |
|---|---|---|---|---|
| 000001 | 1 | 5FUNCTION | 1 | Monitor call function code (e.g., 40₈ = MEMDEF) |
Usage:
IF 5FUNCTION><MEMDEF THEN % Check function code
% ... handle non-MEMDEF functions ...
FI
7.2 MEMDEF Parameters¶
| Offset (Oct) | Offset (Dec) | Symbol | Size | Purpose |
|---|---|---|---|---|
| 000040 | 32 | 5D11 | 1 | Pointer to memory configuration data array |
| 000041 | 33 | 5D12 | 1 | ADRZERO (base page number for 5MPM) |
| 000044 | 36 | 5D22 | 1 | Number of memory parts (max 16₈) |
Usage:
"5D11"+B=:D; X:=ZAREG; OLDPAGE; X+1=:B; T:=3; CALL GND5PAR
IF 5D22>MXMPARTS GO ERROR
5D12=:ADRZERO
7.3 Single-Word Parameters¶
| Offset (Oct) | Offset (Dec) | Symbol | Size | Purpose |
|---|---|---|---|---|
| 000042 | 34 | 5P1 | 1 | Parameter 1 (single word) |
| 000045 | 37 | 5P2 | 1 | Parameter 2 (single word) |
| 000050 | 40 | 5P3 | 1 | Parameter 3 (single word) |
| 000053 | 43 | 5P4 | 1 | Parameter 4 (single word) |
7.4 Double-Word Parameters (Input)¶
| Offset (Oct) | Offset (Dec) | Symbol | Size | Purpose |
|---|---|---|---|---|
| 000100 | 64 | 5AP1 | 2 | Parameter 1 (input, double word) |
| 000102 | 66 | 5AP2 | 2 | Parameter 2 (input, double word) |
| 000104 | 68 | 5AP3 | 2 | Parameter 3 (input, double word) |
| 000106 | 70 | 5AP4 | 2 | Parameter 4 (input, double word) |
Usage:
T:=5MBBANK
*AAX 5AP1; LDDTX % Read parameter 1 (double word)
AD=:PARAM1 % Store in AD register pair
7.5 Double-Word Parameters (Output)¶
| Offset (Oct) | Offset (Dec) | Symbol | Size | Purpose |
|---|---|---|---|---|
| 000101 | 65 | 5DP1 | 2 | Parameter 1 (output, double word) |
| 000103 | 67 | 5DP2 | 2 | Parameter 2 (output, double word) |
| 000105 | 69 | 5DP3 | 2 | Parameter 3 (output, double word) |
| 000107 | 71 | 5DP4 | 2 | Parameter 4 (output, double word) |
Usage:
T:=5MBBANK
PARAM1=:AD % Set AD register pair
*AAX 5DP1; STDTX % Write parameter 1 (double word)
7.6 Parameter Pointers¶
| Offset (Oct) | Offset (Dec) | Symbol | Size | Purpose |
|---|---|---|---|---|
| 000040 | 32 | 5PPA1 | 1 | Pointer to parameter 1 area |
| 000042 | 34 | 5PPA2 | 1 | Pointer to parameter 2 area |
| 000044 | 36 | 5PPA3 | 1 | Pointer to parameter 3 area |
Note: These may overlap with 5D11, 5P1, 5D22 offsets. The meaning depends on context.
8. Summary¶
8.1 Key Points¶
- N500DF is a work area structure in ND-100 memory
- GND5PAR copies parameters from 5MPM message buffer to N500DF
- Parameters are accessed using fixed offsets (e.g.,
5D12,5D22) - Allocation is done via 5RESWORKA (semaphore-protected)
- Release is done via 5RELWORKA (after processing)
8.2 Benefits¶
- No bank setup needed - N500DF is in regular ND-100 memory
- Fixed offsets - Easy to access parameters
- Efficient - Parameters copied once, accessed multiple times
- Thread-safe - Semaphore-protected allocation
8.3 Usage Pattern¶
CALL 5RESWORKA % Allocate N500DF (B = N500DF base)
"5D11"+B=:D; CALL GND5PAR % Copy parameters from 5MPM to N500DF
5D12=:ADRZERO % Access parameter directly
% ... process parameters ...
CALL 5RELWORKA % Release N500DF
End of Document