-- SPIKE (session 34).  Not a gate: it exists to find out whether the chip can be
-- driven at all, what scale its samples arrive at in a -wavwrite capture, and
-- where it clamps.  It sets EVERY thing session 33's probes left to the IPL:
--   * YM2151 reg $1B bit1 = 0  -> CT1 = 0 -> ADPCM master clock 8 MHz
--   * PPI control $92          -> port C is an OUTPUT (without this the i8255's
--                                 out_pc_callback never fires and the pan and
--                                 divider writes go nowhere)
--   * PPI port C  $08          -> pan 00 = BOTH, rate 10 = /512 -> 15,625 Hz
--   * ctrl $02 = COMMAND_PLAY  -- session 33's probes wrote $01, COMMAND_STOP.
M = manager.machine
local sp = M.devices[":maincpu"].spaces["program"]
local YMA, YMD = 0xE90001, 0xE90003
local PPIC, PPICTL = 0xE9A005, 0xE9A007
local CTRL, DATA = 0xE92001, 0xE92003
local BYTE = tonumber(os.getenv("AD_BYTE") or "0x77")
local n = 0
SUB = emu.add_machine_frame_notifier(function()
  n = n + 1
  if n == 40 then
    sp:write_u8(YMA, 0x1B); sp:write_u8(YMD, 0x00)
  elseif n == 60 then
    sp:write_u8(YMA, 0x1B); sp:write_u8(YMD, 0x00)
    sp:write_u8(PPICTL, 0x92)
    sp:write_u8(PPIC, 0x08)
    print(string.format("[AD4] portC readback = $%02X", sp:read_u8(PPIC)))
    sp:write_u8(CTRL, 0x02)
    sp:write_u8(DATA, BYTE)
    print(string.format("[AD4] PLAY, data $%02X, status = $%02X",
                        BYTE, sp:read_u8(CTRL)))
  elseif n == 90 then
    print("[AD4] done"); M:exit()
  end
end)