Skip to content

MON 345B (octal) - MTAFunction (MTAD)

MTA terminal-line function (manual sections 2.14 / 2.17; short name MTAD, also printed as MTADFunction). Connects or disconnects a terminal line to a datafield. Internal-use call; not intended for user programs. This is an ND-100 monitor call.

Status: documented (fall-through). GOTAB[345B] = 000000 (byte-proven) - a fall-through: there is no direct GOTAB handler word, so the level-14 handler is reached through the resident MFELL/CALLPROC path (uncarved). The MTA terminal-line handler exists as real code in overlay 025-S3IRPIT near the MTSTA symbol, but the fall-through bridge to it is uncarved and the exact worker is not statically isolable from these bytes. MTSTA is shown as a candidate (real bytes) only, attributed by the symbol-name family, not a followed pointer (see Honest caveats). All addresses/values are octal.

Dispatch path

flowchart LR
    A["System program<br/>MON 345B"] --> B["ENT14 level-14<br/>T = MON number"]
    B --> C["GOTAB[345B] = 000000<br/>(fall-through, byte-proven)"]
    C -.uncarved MFELL / CALLPROC.-> D["MTA terminal worker<br/>(uncarved; not isolated)"]
    D --> E["MTSTA candidate region<br/>025-S3IRPIT :64636B (real bytes)"]
    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 MFELL/CALLPROC fall-through - not present in any carved segment, so it cannot be followed statically. GOTAB[345B] is literally 000000, so there is no entry stub to disassemble. MTSTA (E) is a real-bytes terminal-line routine in the same overlay, offered as a candidate for the worker family, not a proven target.

Code location (dispatch path)

Every row is a real region you can open. Byte offset = (addr − loadbase) in octal words × 2 (decimal); commoncode load base is 0, 025-S3IRPIT load base is 32000B.

Role Segment (full disasm) Addr range (octal) Byte offset Symbol Verdict
GOTAB[345] dispatch word commoncode.asm · .hex 071600B (1 word) 59136 GOTAB+345 = 000000 VERIFIED (fall-through)
resident MFELL/CALLPROC bridge — (uncarved) — — MFELL/CALLPROC UNVERIFIED
MTSTA candidate terminal region 025-S3IRPIT.asm · .hex 64636B-64647B (real bytes) 27452 MTSTA real bytes; link MISATTRIBUTED

There is no entry-stub row: GOTAB[345] is 000000, so the level-14 handler is a resident fall-through, not a 025-S3IRPIT stub.

Verify by hand (GOTAB word): grep '^71600 ' ../../segments-ref/SINTRAN-DATA_commoncode/SINTRAN-DATA_commoncode.hex → 71600 000000 000 000 59136; then dd if=../../../resident/SINTRAN-DATA_commoncode.bin bs=1 skip=59136 count=2 2>/dev/null | od -An -tx1 → 00 00 (the zero = fall-through). prove-mon.py 345 reads the same GOTAB zero.

Verify by hand (MTSTA candidate): grep '^64636 ' ../../segments-ref/025-S3IRPIT/025-S3IRPIT.hex → byte offset 27452, value 135026; then dd if=../../../segments/025-S3IRPIT.bin bs=1 skip=27452 count=2 2>/dev/null | od -An -tx1 → ba 16 (= octal 135026, JPL I 26, the candidate region's first word - real code).

Instruction walkthrough

Full listing: 345B-MTAFunction.ASM. There is no entry stub (fall-through dispatch), so there is no in-path walkthrough for the dispatch head.

GOTAB[345] = 000000 (fall-through) — the dispatch word is zero; dispatch enters the resident MFELL/CALLPROC handler, which is uncarved.

MTSTA candidate region (64636-64647) — real code: JPL I 26 -> [064664] runs a setup worker, then LDA ,B 21 / STATX and LDA ,B 23 / STATX write two terminal-line status words to the device via the physical device-status transfer STATX, and control returns through a caller link word (JMP I ,B 42). This is consistent with a terminal-line connect/disconnect routine, but its link to MON 345B is not byte-proven - it is attributed by the MTSTA/MTSTART name family only.

Parameter / register contract

Manual-side names/types are from 345B_MTAFunction.yaml (the yaml declares no user-visible parameters - an internal-use call).

Reg / field Dir Meaning Verdict
(internal) — connect/disconnect a terminal line to a datafield inferred (manual sections 2.14 / 2.17)
,B 21 / ,B 23 work terminal-line status words written via STATX (in the MTSTA candidate) VERIFIED bytes (64637-64642); MON 345 link not proven
caller convention in register/CALLG mapping not confirmed from the available source UNVERIFIED

Because GOTAB[345] is zero and the worker sits past the uncarved fall-through, nothing in the user-visible contract is byte-proven for this call.

Pseudo-code (for an emulator)

See 345B-MTAFunction.pseudo.c — a pseudo-C model for emulator authors. Because GOTAB[345] is a fall-through and the real MTA worker sits past the uncarved MFELL/CALLPROC, the model is of the documented behaviour only (connect/disconnect a terminal line to a datafield), NOT the carved code. The MTSTA candidate is modelled separately as real bytes, flagged not-proven. The fall-through MON 345 -> worker bridge is modelled but not proven.

Instruction semantics follow the canonical reference: ../../instruction-semantics/ND100-INSTRUCTION-SEMANTICS.md (STATX = phys[EL] = A with EL = ((T & 0xFF) << 16) | ((X + disp) & 0xFFFF), a 24-bit physical device transfer; RADD CLD 0 DA = A = 0; JMP I ,B 42 = jump through mem[B+42]).

Honest caveats

What is byte-proven: GOTAB[345B] = 000000 (level-14 fall-through; prove-mon.py 345 reads commoncode file byte 0xe700 = 00 00). That is the only fact these carved bytes establish for the dispatch of this call. Separately, the MTSTA region at 64636B is real code (first word 135026 = JPL I 26) that drives terminal-line status via STATX.

What is NOT proven: that MTSTA is the MON 345B worker, and any link from the fall-through to it. Because GOTAB[345] is 000000, there is no stub to follow; dispatch enters the resident MFELL/CALLPROC handler in an uncarved overlay. The yaml names the handler MTSTART (MP-P2-TERM-DRIV.NPL), and the carved MTSTA symbol is a plausible name-family match with real terminal-line code, but that is inferred, not a followed pointer - hence MISATTRIBUTED for the candidate.

This reconciles into one story: the dispatch head (GOTAB[345]=0, fall-through) is solid; the MTA terminal-line code exists in 025-S3IRPIT (MTSTA and neighbours are real bytes); but the exact MON 345 -> worker link crosses the uncarved fall-through and is not isolable from these bytes. Confirming the actual worker needs a live trace (break on a real MON 345, single-step the fall-through, and record where P lands).

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