prosolis
6dd3fb3597
ROADMAP P6a, on the machine. 68000 code programs HD63450 channel 3 with the IPL ROM's own ADPCM bytes -- dual address, 8-bit port, cycle steal, external request -- and feeds the MSM6258 a designed 1,678-nibble stream at the chip's own pace: 839 B in 0.1074 s = 7,811.4 B/s against the format's 7,812.5, CER=$00. That transport is P6b's, not scaffolding. Sixteen candidate decoder models, three capture decimations and a searched prologue are fitted to MAME's capture. Exactly one reproduces it sample-exact over all 1,678 samples, and every axis carries a negative control: flip it alone and the closest survivor disagrees on 826, 1,504, 156 and 1,522 samples. The chip runs 'terms', takes the LOW nibble of a byte first, clamps the accumulator at 10 bits and starts it at -2. tools/encoder/adpcm.py defaulted to the opposite of all four, and 65.2 named the wrong axis as the risk: the delta formula is worth -2.88 dB and the NIBBLE ORDER is worth -25.74 dB. 65.1's "high first, measured" was a measurement of ffmpeg, i.e. of the VOX file convention, which is a different question from what a chip does with a byte in its data register. The 10-bit clamp is free on the Singe window and only because that window peaks at 435 of 511 -- 1.4 dB of headroom on a -13.4 dBFS passage, 12.1 dB below where the encoder was clamping, and inside the recursion. So the audio level is an open choice again, downward, and the loudest passage on the disc is unmeasured. Session 33's silence had two ordinary causes: the PPI's port C is an input until control word $92 says otherwise, and $01 is COMMAND_STOP. And a rig fact worth the space: the 8 MHz ADPCM clock is CT1 in the YM2151's $1B, delivered on the sound system's schedule rather than at the store, so a transfer started in the same breath as the setup plays its first ~17 ms at the old clock and no model fits a stream that changed rate part way through. Name the layer: this is MAME 0.277's okim6258 device model measured end to end through the machine's real transport. It settles the rig and not the silicon. Also struck: 64.4's "no MAME source tree is on this machine" -- there is none on disk, but the machine has network and the upstream tag fetches. check.sh ALL GREEN before (tmp/check_s34_start.log) and after (tmp/check_s34_end.log), with one new stage. Claude-Session: https://claude.ai/code/session_01194oWYW8DQXK1SZ2DnChW6
34 lines
1.5 KiB
Lua
34 lines
1.5 KiB
Lua
-- SPIKE (session 34). Not a gate: it exists to find out whether the chip can be
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-- driven at all, what scale its samples arrive at in a -wavwrite capture, and
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-- where it clamps. It sets EVERY thing session 33's probes left to the IPL:
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-- * YM2151 reg $1B bit1 = 0 -> CT1 = 0 -> ADPCM master clock 8 MHz
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-- * PPI control $92 -> port C is an OUTPUT (without this the i8255's
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-- out_pc_callback never fires and the pan and
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-- divider writes go nowhere)
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-- * PPI port C $08 -> pan 00 = BOTH, rate 10 = /512 -> 15,625 Hz
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-- * ctrl $02 = COMMAND_PLAY -- session 33's probes wrote $01, COMMAND_STOP.
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M = manager.machine
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local sp = M.devices[":maincpu"].spaces["program"]
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local YMA, YMD = 0xE90001, 0xE90003
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local PPIC, PPICTL = 0xE9A005, 0xE9A007
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local CTRL, DATA = 0xE92001, 0xE92003
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local BYTE = tonumber(os.getenv("AD_BYTE") or "0x77")
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local n = 0
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SUB = emu.add_machine_frame_notifier(function()
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n = n + 1
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if n == 40 then
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sp:write_u8(YMA, 0x1B); sp:write_u8(YMD, 0x00)
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elseif n == 60 then
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sp:write_u8(YMA, 0x1B); sp:write_u8(YMD, 0x00)
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sp:write_u8(PPICTL, 0x92)
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sp:write_u8(PPIC, 0x08)
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print(string.format("[AD4] portC readback = $%02X", sp:read_u8(PPIC)))
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sp:write_u8(CTRL, 0x02)
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sp:write_u8(DATA, BYTE)
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print(string.format("[AD4] PLAY, data $%02X, status = $%02X",
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BYTE, sp:read_u8(CTRL)))
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elseif n == 90 then
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print("[AD4] done"); M:exit()
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end
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end)
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