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https://git.k-space.ee/arti/vt1200.git
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SDD
1608a68cdb
An 82-byte payload written in GSPA assembly, linked at bit 01800000h and loaded into main RAM by harness/mame/hello.lua, executes on the CPU: it writes DEAD/BEEF and a 1024-iteration counter into RAM and fills a 256x64 block in video RAM, which appears in the frame dump at x 256..511, y 136..199. Entry is a debugger breakpoint on the level-0 menu idle loop, not a delivery mechanism. Includes the build script, a COFF .text extractor (gsprom's hex addresses wrap at 64 KB), the run log, RAM excerpt, frame crops including a no-load control, and HELLO_WORLD_REPORT.md.
53 lines
1.7 KiB
NASM
53 lines
1.7 KiB
NASM
; hello.asm -- minimal TMS34010 payload for the VT1200 harness.
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;
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; Built with GSPA 2.00 / GSPLNK 2.00 (1987 TI SDK, DOSBox) and linked at
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; bit address 01800000h (byte 00300000h in main RAM).
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;
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; It leaves two independent pieces of evidence:
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; 1. RAM: two magic words and a loop counter at bit 01810000h.
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; 2. VRAM: a solid 256x64 block at framebuffer row 100, column 64.
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;
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; The screen renderer (harness/mame/vt1200.cpp, render_active_line) reads
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; VRAM at bit 04000000h with a row pitch of 1024 bits and bit 0 = leftmost
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; pixel, LSB-first inside each 16-bit word.
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;
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; Addresses in operands are BIT addresses, like every TMS34010 pointer.
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; A 16-bit pixel row is 64 words; we write 16 words (256 pixels) and then
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; advance the destination by 1024 - 256 = 768 bits (0300h).
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.text
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_start:
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dint ; stay deterministic: no firmware ISR
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setf 16, 0, 0 ; field 0 = 16 bits, zero-extended
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setf 32, 0, 1 ; field 1 = 32 bits, zero-extended
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; ---- channel 1: RAM markers -----------------------------------
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movi 0DEADh, a0, L
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move a0, @01810000h, 0 ; MAGIC1 (bytes AD DE in a dump)
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movi 0BEEFh, a0, L
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move a0, @01810010h, 0 ; MAGIC2 (bytes EF BE)
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; ---- channel 2: solid block in video RAM ----------------------
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movi 04019040h, a2, L ; 04000000h + 100*1024 + 64
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movi 64, a3, L ; 64 rows
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movi 16, a4, L ; 16 words = 256 pixels per row
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sub a1, a1 ; counter = 0
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movi 0FFFFh, a0, L
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row_loop:
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move a4, a5
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word_loop:
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move a0, *a2+, 0 ; store word, postincrement by 16 bits
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addi 1, a1 ; count this store
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dsjs a5, word_loop
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addi 0300h, a2 ; skip 768 bits to the next row
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dsjs a3, row_loop
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; The counter is 0400h only if all 64*16 stores executed.
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move a1, @01810020h, 0 ; COUNT
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spin:
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nop
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jruc spin
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.end
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