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https://git.k-space.ee/arti/vt1200.git
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SDD
634246ecb1
Milestone 1 of docs/superpowers/plans/2026-10-16-lance-ethernet.md.
Modelled:
* MAME am79c90 (AM79C90) at the firmware's two windows -- bit 0x5900000 is
RAP, 0x5800000 is RDP; every other offset in those windows still falls
through to the board model.
* the Ethernet address ROM at bit 0x6800000, as EIGHT bytes. The plan said
six; the firmware's reader (0x3FDD7520) actually loops i = 0..7 and then
validates a folded ones-complement checksum over bytes 0..5 against
bytes 6..7 (0x3FDD78B0). For the MAC 08:00:2b:16:4b:5a that is 0xC186, so
the ROM is 08 00 2b 16 4b 5a c1 86. A six-byte ROM returns expected = 0
and fails LEVEL1/2 ERROR -> ETHERNET ROM CHECKSUM - 23. The checksum
bytes are derived from the firmware's own algorithm (documented in
LANCE_REPORT.md); they are not read off a real PROM.
* the interrupt on INT1, matching the ISR 0x3FA93400 and INTENB bit 1.
* bus-master DMA, translating the LANCE's byte address to the TMS34010's
bit-addressed main RAM (byte B -> word B>>1), cross-checked against the
firmware's own CSR1 = 0xFF60 = RAM word 0x7FB0.
* VT1200_LANCELOG to trace the register/ROM accesses.
Observed with the firmware's own diagnostics menu (driven by the real LK401
model; new menu_keys.lua): the M -- ETHERNET ROM TEST now PASSES. The
C -- LANCE TEST runs the chip for real -- the firmware's init block
(mode 0x004C = LOOP|INTL|DTCR, PADR 08:00:2b:16:4b:5a) is read via the new DMA,
INIT completes (CSR0 = 0x6FE3, IDON), the chip transmits and receives -- but its
internal-loopback receive still reports a CRC error under MAME (RCV descriptor
1 = 0x4B00, message count 0). Cause: MAME's receive() runs the FCS check when
MODE_LOOP && MODE_DTCR (am79c90.cpp:263) even though DTCR means no FCS was
appended. No MAME change was made; quoted and reported in LANCE_REPORT.md.
The OS (skip gate) reads the ROM MAC, programs CSR1/2/3, INITs, sees IDON,
STRTs and polls CSR0; the Terminal Manager now shows Ethernet Address
08-00-2B-16-4B-5A (was 00-00-00-00-00-00) and LAT_08002B164B5A.
Baselines unchanged: no-env samples=198 (3 PCs), VT1200_IO_PATH_STUB samples=53
(75 PCs). ROM md5 unchanged. No MAME tree changes.
62 lines
1.8 KiB
Lua
62 lines
1.8 KiB
Lua
-- menu_keys.lua -- drive the level-0 diagnostics menu with the modelled LK401
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-- keyboard, to run a selected test through the firmware's own test map.
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--
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-- MENU_KEYS=C,Z MENU_AT=300 MENU_DUMP=200,800 \
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-- <mame> vt1200 ... -video none -nothrottle -debug -debugger none \
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-- -autoboot_script harness/mame/menu_keys.lua
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--
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-- MENU_KEYS is a comma list of single characters (LK401 keycaps). Each is
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-- pressed for MENU_HOLD frames (default 6), MENU_GAP frames apart (default 30).
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local machine = manager.machine
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local ports = machine.ioport.ports
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-- LK401 port index by character (VT1200_LK401_KEY_LIST order).
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local KEY = {
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["C"] = ":lk401:K40", ["Z"] = ":lk401:K38", ["M"] = ":lk401:K44",
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["O"] = ":lk401:K21", ["Q"] = ":lk401:K13", ["X"] = ":lk401:K39",
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}
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local keys = {}
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for k in string.gmatch(os.getenv("MENU_KEYS") or "C,Z", "([^,]+)") do
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keys[#keys + 1] = k
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end
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local at = tonumber(os.getenv("MENU_AT") or "300")
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local hold = tonumber(os.getenv("MENU_HOLD") or "6")
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local gap = tonumber(os.getenv("MENU_GAP") or "30")
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local last = tonumber(os.getenv("MENU_LAST") or "1500")
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-- schedule: key i pressed at at + i*gap
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local frame = 0
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local function set_key(k, v)
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local tag = KEY[k]
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if not tag then print("MENU unknown key " .. k); return end
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local port = ports[tag]
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local f
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for _, field in pairs(port.fields) do f = field end
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if f then f:set_value(v) end
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end
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emu.register_frame_done(function()
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frame = frame + 1
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for i, k in ipairs(keys) do
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local t = at + (i - 1) * gap
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if frame == t then
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set_key(k, 1)
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print(string.format("MENU frame=%d press %s", frame, k))
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elseif frame == t + hold then
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set_key(k, 0)
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end
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end
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if frame >= last then
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machine:exit()
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end
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end, "vt1200-menu-keys")
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local dbg = machine.debugger
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if dbg then
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dbg.visible_cpu = machine.devices[':maincpu']
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dbg.execution_state = 'run'
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end
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