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MON 304B (octal) — SendSIBASMessage (MAPSI)

Sends a request message to a SIBAS database server (ND-100 RT-common or the ND-500) and receives its answer, blocking the caller until SIBAS replies. NOTE: this is MON 304B — the manual's "Performance 304B" is an OCR error (Performance is 344B).

Status: the GOTAB dispatch word is byte-proven, but it does not point at the SIBAS handler. GOTAB[304] = 112065B (live + byte proven) lands on DSI0/XBUSA in the DSI/DIA block; the semantic MAPSI SIBAS worker is real SINTRAN L bytes but is unreachable from GOTAB[304] and from every GOTAB slot 0..377 — it is reached only across the uncarved resident CALLPROC bridge (see Honest caveats). All addresses/values are octal.

Dispatch path

flowchart LR
    A["User program<br/>MON 304B"] --> B["ENT14 level-14<br/>T = MON number"]
    B --> C["GOTAB[304B] = 112065B<br/>(byte + live proven)"]
    C --> D["DSI0/XBUSA stub<br/>025-S3IRPIT :112065B"]
    D --> E["DIA0 body<br/>025-S3IRPIT :111771B"]
    C -.uncarved CALLPROC.-> F["MAPSI SIBAS worker<br/>025-S3IRPIT :103675B"]
    class A blue
    class B,C,D teal
    class E green
    class F 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 solid edge (C → D → E) is byte-proven: GOTAB[304] = 112065B = DSI0, a 2-word stub (ION / JMP -75) that jumps into the DIA0 body at 111771B. The dashed hop (C ⇢ F) is the resident CALLPROC/second-level dispatch to the semantic MAPSI SIBAS handler — it is not present in any carved segment, so it is the one link that cannot be followed statically.

Code location (dispatch path)

Ground truth: python3 scripts/prove-mon.py 304 → GOTAB[304] = 112065B (big-endian 94 35). Byte offset of octal address A in a segment with load base L: word = (A − L) in octal, byte = word × 2 (decimal). Rows are in execution order; DISPATCH.md's byte-verdict wins.

Role Segment (full disasm) Addr range (octal) Byte offset Symbol Verdict
GOTAB[304] dispatch word commoncode.asm · .hex 071537B (1 word) 59070 GOTAB+304 = 112065B VERIFIED (raw word 94 35)
DSI0/XBUSA entry stub 025-S3IRPIT.asm · .hex 112065B–112066B 49258 DSI0/XBUSA VERIFIED (150402 ION; 124303 JMP -75 → 111771B)
DIA0 body (entered at 111771B) 025-S3IRPIT.asm · .hex 111752B–112113B 49108 DIA0 bytes VERIFIED; semantics UNVERIFIED (issues MON 131/64/116/134 — RT-level, not clean L14)
resident CALLPROC bridge — (uncarved) — — CALLPROC UNVERIFIED
MAPSI SIBAS worker body 025-S3IRPIT.asm · .hex 103675B–104351B 42874 MAPSI/MSIBB/TISIB real bytes; link MISATTRIBUTED (unreachable from GOTAB[304] and every slot 0..377)

Verify by hand: grep '^71537 ' ../../segments-ref/SINTRAN-DATA_commoncode/SINTRAN-DATA_commoncode.hex → 71537 112065 224 065 59070 (word 112065B, byte offset 59070); then dd if=../../../resident/SINTRAN-DATA_commoncode.bin bs=1 skip=59070 count=2 | od -An -tx1 → 94 35. For the DSI0 target: dd if=../../../segments/025-S3IRPIT.bin bs=1 skip=49258 count=2 | od -An -tx1 → d1 02 (= octal 150402, ION, the DSI0 stub head).

Instruction walkthrough

Full listing: 304B-SendSIBASMessage.ASM. Two regions.

Region A — the byte-proven GOTAB target (DSI0 → DIA0 body). GOTAB[304] = 112065B = DSI0/XBUSA, a 2-word stub: 

112065  150402  ION
112066  124303  JMP -75        ; -> 111771B, into the DIA0 body
The DIA0 body (111752B–112113B) reads a status/flags word (111771 LDT ,B 33), branches on its bits, and on the main path does a block transfer: 112016 ION / 112021 MON 131 (ABSTR / DataTransfer) / 112023 IOF. Its error path (112077–112112) issues MON 64 (ERMSG), MON 116 (UNFIX) and MON 134 (RTEXT); the tail (112055–112064) uses IRW 20 DP / MST PID (RT scheduling). ANOMALY: issuing MON and using IRW/MST PID is resident RT-program/driver behaviour, not clean level-14 handler code — hence the DIA0 semantics are UNVERIFIED pending a live trace (the stub→body edges are byte-solid).

Region B — the semantic SIBAS handler (MAPSI). MAPSI at 103675B decodes as a clean level-14 SIBAS handler and issues no MON instructions: 

103675  146173  RADD CLD SX DB   ; X=:B
103676  170404  SAA 4            ; MLEV
103677  150207  MCL PIE          ; *MCL PIE
103706  044411  LDA ,B 11        ; fetch ZTREG (SIBAS device number)
103707  051150  LDT I 150        ; MXSIB
103710  141456  SKP IF DT MGRE SA ; IF ZTREG > MXSIB -> error exit
It then locates the SIBAS device block, copies the request into RT-common (104051 MOVEW, MOVAP-style), reactivates the SIBAS server, blocks for the reply, copies the answer back (104170 MOVEW, MOVPA-style), and stages the result (174 bad size, -1/-2/-3 errors, 0 OK) into ,B 12 before returning (104216 STA ,B 12 / 104220 JMP I). MSIBB=104221B and TISIB=104315B are sibling entries in the same body. This matches the NPL SUBR MAPSIB,MSIBB,TISIBB structure — but it is not what GOTAB[304] reaches.

Parameter / register contract

Reg / field Dir Meaning Verdict
ZTREG (,B 11) in SIBAS device number (≤ MXSIB, checked at 103710) VERIFIED bounds check; slot mapping inferred
ZXREG in address of message (length in word S1, max 177×4) inferred (NPL contract)
ZAREG (,B 12) out 0 OK; -1/-2/-3 errors; 174 bad size (staged 104207–104216) VERIFIED result-code stores; meaning inferred
entry point in MAPSI=103675B (message xfer); MSIBB=104221B, TISIB=104315B siblings VERIFIED (bytes)
GOTAB target dispatch GOTAB[304]=112065B → DSI0, not MAPSI VERIFIED (byte + live)

The user-visible register convention lives in the caller-side MON 304 wrapper and the uncarved CALLPROC frame, so the precise A/X/T assignment for MAPSI is inferred, not byte-proven.

Pseudo-code (for an emulator)

See 304B-SendSIBASMessage.pseudo.c — a pseudo-C model with BOTH paths: dispatch_DSI0() (the byte-proven GOTAB target, RT-level semantics UNVERIFIED) and mon_send_sibas_message() (the semantic MAPSI SIBAS handler). Control flow and the SIBAS bounds-check/MOVEW copies are byte-verified; the register/parameter labels are inferred from the NPL structure.

Every instruction in the .pseudo.c is translated against the canonical ND100-INSTRUCTION-SEMANTICS.md (SKP IF DT MGRE SA = skip if T >= A UNSIGNED - the MXSIB/dev bounds test; LDT I 150 is an indirect fetch, 150 is the displacement not the value; RADD CLD SA Dx = x = A).

Honest caveats

What is byte-proven: GOTAB[304] = 112065B (matches a live read of the running system); 112065B is DSI0/XBUSA, a 2-word stub (ION / JMP -75) that jumps into the DIA0 body at 111771B; those stub→body edges resolve in-segment. The MAPSI worker entry bytes at 103675B are real SINTRAN L bytes and decode as a clean SIBAS handler.

What is NOT proven — one story reconciling ANALYSIS vs DISPATCH: the original folder attributed MON 304B to MAPSI=103675B (the SIBAS handler). Byte-truth says otherwise. GOTAB[304] points to DSI0, and three independent byte checks show MAPSI is unreachable from it: 1. DSI0 (112065) → MAPSI (103675) is ~6000B words apart — far outside any ND-100 relative JMP/JPL displacement, so no direct edge is possible. 2. A full word-scan of 025-S3IRPIT.bin for any word equal to 103675/104221/104315 (an absolute JMP I/JPL I pointer to MAPSI/MSIBB/TISIB) returns zero matches. 3. A full GOTAB[0..377] scan for any value inside the MAPSI window returns none — no MON call 0..377 dispatches to the carved worker.

So MAPSI is real code reached only through the resident CALLPROC second-level dispatch, which lives in an uncarved overlay — hence MISATTRIBUTED in the strict byte sense. A secondary caveat: even the DSI0 target decodes as RT-level code (MON 131/64/116/134, IRW/MST PID), inconsistent with pure level-14 handler semantics for a MON# this high, so the DSI0 attribution is itself UNVERIFIED pending a live trace. Confirming either needs a live level-14 trace: break on a real MON 304B, capture the first PC after the trap, and see whether it lands on 112065B (DSI0), 103675B (MAPSI), or enters CALLPROC then a second-level table — and whether the resident GOTAB indexed at 071233B truly covers a MON# this high or a separate RT/start table backs these indices.

Address note: the NPL source is a different revision (NPL MAPSIB=103476B vs L07 MAPSI=103675B). Match behaviour/structure, not raw bytes.

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