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MON 515B (octal) - MultipleDataTransfer (5MTRA)

Queues / checks / starts a multiple disk data transfer for an ND-500 process, mapping the process's logical device + read/write function onto the ND-100 disk driver queue.

Status: worker body is real SINTRAN L bytes (symbol 5MTRA = 143445B, byte-verified); this is an ND-500 level-12 GOSW call, NOT an ND-100 GOTAB slot - the GOSW-index-13 to 5MTRA table lookup is resident and not byte-located (see Honest caveats). All addresses/values are octal.

Dispatch path

flowchart LR
    A["ND-500 process<br/>MON 515B"] --> B["stop MOCALL,<br/>enter level-12"]
    B --> C["MCHANDEL reads<br/>call number 515B"]
    C -.uncarved GOSW table.-> D["5CMNO GOSW index 13"]
    D --> E["5MTRA worker body<br/>026-S3IMPIT :143445B"]
    class A blue
    class B,C blue
    class D teal
    class E green
    classDef blue fill:#E3F2FD,stroke:#0D47A1,color:#0D47A1
    classDef teal fill:#E0F7FA,stroke:#00838F,color:#00838F
    classDef green fill:#E8F5E9,stroke:#2E7D32,color:#2E7D32

The dashed hop (C ⇢ D) is the resident level-12 GOSW table lookup - it is not present in any carved segment, so the index-13 to 5MTRA selection cannot be followed statically here. It is inferred from the ND-500 dispatch structure, not byte-proven.

Code location (dispatch path)

Every worker row is a real region you can open. Byte offset = (addr − loadbase) in octal words × 2.

Role Segment (full disasm) Addr range (octal) Byte offset Symbol Verdict
ND-100 GOTAB[515] neighbour (WRONG namespace) commoncode.asm · .hex 071750B word = 057605B 59344 GOTAB+515 → T109R MISATTRIBUTED (ND-100 IO routine, not this call)
level-12 GOSW table lookup — (resident, uncarved) — — 5CMNO+13 UNVERIFIED (index inferred)
level-12 worker body 5MTRA 026-S3IMPIT.asm · .hex 143445B–143643B (127 words) 75338 5MTRA VERIFIED (real bytes)

prove-mon.py 515 walks the ND-100 GOTAB and lands on T109R = 057605B - a different, unrelated ND-100 IO routine in another dispatch namespace that merely shares the number 515. The row above lists it only to mark it MISATTRIBUTED so no one mistakes it for this handler.

Verify by hand (the real 5MTRA entry): grep '^143445 ' ../../segments-ref/026-S3IMPIT/026-S3IMPIT.hex → byte offset 75338; then dd if=../../../segments/026-S3IMPIT.bin bs=1 skip=75338 count=8 | od -An -tx1 → 1a 62 02 62 cc 5d 0a 61 (= octal 015142 001142 146135 005141 …, the STX I 142 / STZ I 142 / RADD SB DA / STA I 141 prologue).

Verify the MISATTRIBUTED GOTAB word: dd if=../../../resident/SINTRAN-DATA_commoncode.bin bs=1 skip=59344 count=2 | od -An -tx1 → 5f 85 (= octal 057605B = T109R, not this handler).

Instruction walkthrough

Full listing: 515B-MultipleDataTransfer.ASM. One region, the 5MTRA worker body. Control flow is byte-verified; the semantic labels are inferred from instruction shape.

Entry prologue (143445–143456) - save context, fetch the descriptor. On entry B holds the ND-500 message/control-block base (143447 RADD SB DA copies it into A immediately, then 143450 STA I 141). A double-word field at base+100B is fetched (AAX 100 / LDDTX) and its low word kept in A.

Validity gate (143457–143460). BSKP ONE 0 DA tests a bit of A; on failure 143460 JMP I 135 -> 143615 branches to the exit fix-up path.

Range / function classification (143461–143512). Reloads a sub-field (AAX 110 / LDATX), calls a shared worker (143463 JPL I 133 -> 143616, indirect), then a cascade of LDT <const> / SKP IF DX MGRE|MLST ST / JMP comparisons against bounds 132 / 130 / 126 / 117, building a function selector in A (SAA 1, RADD CLD 0 DA). This is the classic "is the requested function/sector inside the legal window?" ladder. Out-of-range takes: 

143513  SAA 6             ; A := 6  (status/err 6)
143514  JMP I 111         ; -> 143625  (exit fix-up)

Queue-slot handling (143515–143546). With a valid classification it stores the slot index (STX I 111 / LDX 111), loads a per-device slot word (LDA ,X 13) and branches on a busy/free flag (143520 JAF 27 -> 143547). The FREE fall-through issues a burst of indirect worker calls (JPL I 106/105/104 -> 143630/143631/143632/143633) interleaved with RAND 0 0 guards, builds a transfer descriptor (LDT I 62 / AAX 147 / LDATX / … / STDTX), does the sector arithmetic (SAD 6 / SUB I 73 / SAD ZIN SHR 5) and hands off: 

143545  STD I 70
143546  JMP I 71          ; -> 143637  (enqueue / start-transfer worker)

Already-active branch (143547–143606). Decrements an outstanding-count field (LDA ,B 13 / AAA -1 / STA ,B 13), then decodes a device status word (LDX I 30 / LDT I 32 / AAX 111 / LDATX / AND 56) onto ND-500 return-status codes via a SAT n / SKP IF DA EQL|UEQ ST / JMP decision tree. The SAT immediates seen (60, 1, 7, 61, 6, 66) are the candidate status values. Terminates with 143605 SAA 7 / 143606 JMP I 17 -> 143625.

Exit / fix-up tail (143607–143643). A mix of pointer words and short store sequences (STT I …, STF I ,B 41, SWAP SP DD) that restore the ND-500 message-buffer / process fields and post the status word before returning to MCHANDEL. The last executable line is an indirect call 143637 JPL I 67 -> 143726, a shared worker OUTSIDE this window (excluded from closure - see Honest caveats).

Parameter / register contract

ND-500 level-12 calls pass arguments in the process's message/control block, not in ZAREG/ZXREG/ZTREG.

Reg / field Dir Meaning Verdict
B = message/control-block base in 143447 RADD SB DA, 143450 STA I 141; every field access is ,B/I 141 relative VERIFIED (bytes)
double-word field at base+100B in 143452 AAX 100 / 143453 LDDTX VERIFIED offset; meaning inferred
function/sector value in DX in bounds ladder SKP IF DX MGRE/MLST ST vs 132/130/126/117 VERIFIED compared; semantics inferred
per-device slot word base+13B in/out 143517 LDA ,X 13; 143552/143554 decrement VERIFIED (bytes)
device status word (via I 30/I 32) in 143557 LDX I 30 / 143560 LDT I 32 / 143562 LDATX / 143564 AND 56 VERIFIED (bytes)
return status in A out SAA 1/6/7, SAT 60/1/7/61/6/66 written then stored VERIFIED literals exist; exact mapping inferred

Return-status literals seen (octal): 1, 6, 7 (via SAA) and 60, 61, 66 (via SAT). The older note "status 1/2/4 or errors 6/7" is only partly consistent - 2 and 4 are not present as literals in this window (UNVERIFIED). The 5MNWA/5MFNC/5MLGN/5MDIS/5MEMA/5DSEC/5MNOS/5MREQ message-field names are plausible labels but were not resolved to byte offsets from ground truth here - treat them as UNVERIFIED behaviour hints.

Pseudo-code (for an emulator)

The pseudo-C is grounded in the ND-100 instruction-semantics reference ../../instruction-semantics/ND100-INSTRUCTION-SEMANTICS.md: the T/X transfers are 24-bit physical accesses EL = ((T & 0377) << 16) | ((X + disp3) & 0177777) (T = the bank, MMU-bypassed), and RADD CLD Sx Dy = y = x. For this memory-transfer call those physical transfers are the core of the handler.

See 515B-MultipleDataTransfer.pseudo.c - a pseudo-C model of the handler for emulator authors. The control flow (validity gate, bounds ladder, busy/free fork, status decode) is byte-verified; the field and status-code semantics are inferred from instruction shape, not from a manual or a symbol-resolved field map.

Honest caveats

What is byte-proven: the worker bytes at 143445B..143643B are real SINTRAN L bytes for 5MTRA (L07 symbol 5MTRA = 143445B, SINTRAN/NPL-SOURCE/SYMBOLS/L07/SYMBOL-2-LIST.SYMB.TXT:3950); they are non-zero coherent code; every DIRECT branch resolves inside the window; the on-disk bytes match the disassembly line-for-line (regenerated from the canonical segment in this pass).

What is NOT proven: - The dispatch link. This is an ND-500 level-12 GOSW call, dispatched by MCHANDEL through the resident 5CMNO GOSW table at index 13. That table is in an uncarved resident region, so the "index 13 → 5MTRA" selection is inferred from the ND-500 dispatch structure, not a followed pointer. Confirming it needs a live trace (level-12 call 515B, single-step MCHANDEL, confirm P lands on 5MTRA = 143445B). - The number collision. prove-mon.py 515 walks the ND-100 GOTAB and reports T109R = 057605B, a real but unrelated ND-100 IO routine. It cannot see the ND-500 level-12 GOSW table, so for a level-12 call number it necessarily lands on the wrong routine. T109R is MISATTRIBUTED here; it is not this handler. - The out-of-window worker. 143637 JPL I 67 -> 143726 is an INDIRECT call to a shared worker outside the carved window; correctly excluded from closure, its body is not in these bytes. - Source-copy label. The window is cited from 026-S3IMPIT.bin (Image copy); the equivalent Save copy 017-S3SMPIT.bin (both load 32000B) is expected to be byte-identical over this range but was not re-verified byte-for-byte across both files in this pass (UNVERIFIED). - Field / status semantics. The 5M* field names and the exact function-code / status-code meanings are inferred from instruction shape, not resolved from ground truth (see the contract).

Method: ../../../../../EXTRACTING-RESIDENT-CODE.md · dispatch reality: ../../TASK-05-mismatches.md · master map: ../../MON-CALL-INDEX.md.