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MON 511B (octal) - Combined terminal output+input (DVIO)

Writes a prompt string to a terminal and then reads a line of input back into the ND-500 process, returning the number of bytes read - the fused form of DVOUTST (output) + DVINST (input). All addresses/values are octal.

Status: handler identity byte-proven (real SINTRAN L bytes at DVIO=141027B); the level-12 GOSW dispatch that reaches it is an uncarved kernel path; the input phase (byte count / write-back) lives in adjacent code outside this carve (see Honest caveats).

Dispatch path

MON 511B is an ND-500 level-12 monitor call. It is not dispatched through the ND-100 monitor GOTAB - a GOTAB[511] probe lands in the terminal-datafield pointer region (spurious). It arrives at the handler via the level-12 GOSW.

flowchart LR
    A["ND-500 process<br/>MON 511B"] --> B["stop MOCALL<br/>level-12 driver"]
    B --> C["MCHANDEL reads<br/>MCNO = 511B"]
    C -.uncarved 5CMNO GOSW.-> D["DVIO handler<br/>026-S3IMPIT :141027B"]
    D --> E["output phase: OSTRS<br/>then input phase XNINSTR"]
    class A blue
    class B,C teal
    class D,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 (5CMNO-L12MIN, index 9) - it is not present in any carved segment, so it is the one link that cannot be followed statically.

Code location (dispatch path)

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

Role Segment (full disasm) Addr range (octal) Byte offset Symbol Verdict
GOTAB[511] probe (spurious) commoncode.asm · .hex 071744B reads 057531B 59336 T107R (terminal-107 datafield ptr, not code) MISATTRIBUTED - ND-500 call is not in GOTAB
Level-12 GOSW dispatch — (uncarved resident level-12) MCHANDEL reads MCNO=511B; 5CMNO-L12MIN GOSW index 9 — 5CMNO / L12MIN UNVERIFIED - dispatch mechanism, not carved
DVIO handler body 026-S3IMPIT.asm · .hex 141027B–141166B (96 words) 72750 DVIO=141027B (shared entry NOUTS) VERIFIED
Input phase (adjacent) 026-S3IMPIT.asm · .hex ~141072B region (XNINSTR/NECHO) — XNINSTR UNVERIFIED - outside the carved 96-word window

Verify by hand: grep '^141027 ' ../../segments-ref/026-S3IMPIT/026-S3IMPIT.hex → byte offset 72750; then dd if=../../../segments/026-S3IMPIT.bin bs=1 skip=72750 count=8 | od -An -tx1 → ba 33 aa 33 cc 4d 5a 32 (= octal 135063 125063 146115 055062 …, the DVIO entry JPL I 63 / JMP I 63 idiom).

Instruction walkthrough

Full listing: 511B-DVIO.ASM. The 96-word window is two code blocks separated by a pointer/literal pool at 141112..141125; the disassembler mis-renders that pool as instructions (ROP NOOP, STT I, …) - those words are the indirect-jump targets, not executable code.

Pointer pool (141112..141125), resolved against L07 symbols - the decisive identity proof: all seven words resolve one-to-one to DVIO's worker set, in NPL order.

Ptr word Value Symbol (L07, 5-char) Worker
141112 147440 5GTDF get terminal datafield
141113 137167 NORMM NORMMC - non-terminal MON fallback
141117 023021 EMONI EMONICO - restart ND-500 proc w/ error
141120 145466 XACTR XACTRDY - reactivate ND-500 exec queue
141121 135067 NXTMS NXTMSG - handle next ND-500 message
141122 141205 OSTRS OSTRS - output-string restart (level-12)
141124 023670 WN5ST WN5STATUS - write ND-500 process status

Entry / output setup (141027..141055) - 141027 JPL I 63 → 5GTDF (is this a terminal? get its datafield); 141030 JMP I 63 → NORMMC skip-return handles the not-a-terminal case. 141031..141040 build the output-datafield pointer via TODF/STATX/LDDTX and load DNOBY. 141041..141050 range-check the count: DNOBY > 4000B (or negative) → SAA 174 (error EC174) then EMONICO/XACTRDY/ NXTMSG. 141052..141055 a zero-length prompt skips output and enters OSTRS.

Read-data-memory setup (141056..141111) - 141056 LDA,B -10 / BSKP ZRO tests the MIFLAG bit WSMC (buffer already in the COM-buffer?); if not, 141061..141105 build the ND-500 micro-function XMICF = read-data-memory (byte count NRBYT, 5DITN, ND-500 logical addr, ND-100 physical addr, SPFLA restart flag), then WN5STATUS/XACTRDY/NXTMSG.

STTDRIV - start terminal output driver (141126..141166) - 141126 STX -1 saves the message; 141127..141145 index TODF to the terminal output datafield and call XSTDFADDR. 141146 LDA,X3 / BSKP ONE tests TYPRING bit 5BAD: bad line → L12STDV (TAD path), else L3STDV (normal). 141157..141160 store MFUNC; 141161 SAA 14 marks the proc N5IOWAIT; then WN5STATUS / GCPUDF / RTACT start the driver; 141166 JMP I 14 → NXTMSG exits (driver continues asynchronously).

On output completion the terminal driver re-enters level-12 via OSTRS, which for SMCNO=511 runs the input phase (XNINSTR) and reports the returned byte count.

Parameter / register contract

ND-500 monitor calls pass parameters in the ND-500 message buffer (indexed by 5MBBANK + field displacement), not in ND-100 A/T/X user registers. The register use below is level-12 driver-internal.

Item Dir Meaning Verdict
X (entry) in current ND-500 message address (N5MESSAGE) VERIFIED (bytes: N5MESSAGE indexing)
B (entry) in ND-500 CPU datafield inferred (NPL asserts; not provable from this window)
TODF (msg) in output datafield pointer VERIFIED (STATX via TODF index)
DNOBY (msg) in output byte count, max 4000B VERIFIED (range check → EC174)
11DMA / DMAXB (msg) in max input bytes (input phase) inferred - lives in XNINSTR (141072 region), not carved here
11NOCHRET (msg) out number of bytes actually read inferred - written in NECHO/EOF path, outside carve
NUMPAR (msg) out monitor-call write-back mask = 100000B inferred - set in the input phase, outside carve
Error EC174 out illegal output byte count (>4000B or negative) VERIFIED (SAA 174 → EMONICO)
Error 316 out terminal line not connected inferred (NPL only; in XNINSTR)
Error 3 out end-of-file on nowait input inferred (NPL only)

Skip-return: none in the ND-100 sense. Control leaves via NORMMC (not a terminal), NXTMSG (done/error), or the async driver (RTACT).

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 message-buffer bank, MMU-bypassed), and RADD CLD Sx Dy = y = x.

See 511B-DVIO.pseudo.c - a pseudo-C model of the handler for emulator authors. Control flow and the seven indirect worker pointers (141112..141124) are byte-verified; the semantic labels (which worker does what) are inferred from the call structure and the NPL DVIO body (a different revision).

Honest caveats

What is byte-proven: the handler at DVIO=141027B is real SINTRAN L code carved from 026-S3IMPIT (load 32000B). Two independent anchors agree: (1) DVIO=141027 in the L07 symbol table, and (2) all seven indirect pointer words (141112–141124) resolve to exactly DVIO's worker set (5GTDF, NORMMC, EMONICO, XACTRDY, NXTMSG, OSTRS, WN5STATUS) in NPL order. The output-count range check (SAA 174 → EMONICO, error EC174) is byte-verified. The carved slice is byte-identical to the canonical segment (dd above reproduces the entry words).

What is NOT proven: - The dispatch. MON 511 is an ND-500 level-12 call; it is not in GOTAB. The prove-mon.py probe is misleading here - GOTAB[511]=057531=T107R is the terminal-107 datafield pointer, not a handler. The real path is the resident level-12 GOSW (MCHANDEL reads MCNO, 5CMNO-L12MIN index 9), which is in an uncarved overlay and cannot be followed statically. - The input phase. 11DMA, 11NOCHRET, NUMPAR, error 316 and EOF-error 3 are set in XNINSTR/NECHO, adjacent code outside the 141027..141166 window - hence marked inferred. A follow-up carve of the NINSTR/XNINSTR block would close this. - The pool. Words 141112..141125 in the .ASM are data (indirect-jump targets), not the ROP NOOP/STT I instructions the disassembler prints. - NPL is a different revision than L. NPL places DVIO at 140627; the L bytes place DVIO=141027. Only the behaviour and worker names carry over - the worker names were re-verified against the L07 pointer words above.

Confirming the full chain needs a live trace (break at the level-12 GOSW on a real ND-500 MON 511, single-step, confirm P lands on DVIO=141027).

Method: ../../../../../EXTRACTING-RESIDENT-CODE.md §7.6/7.7 · dispatch reality: ../../TASK-05-mismatches.md · master map: ../../MON-CALL-INDEX.md.