checkpoint: VT1200 reverse-engineering workspace before board-model work

harness/mame/stackwalk.lua

@@ -0,0 +1,52 @@
+-- When the CPU is parked in the POST delay loop, dump the stack so we can see
+-- the caller chain -- i.e. who passes the absurd delay count, and where the
+-- count comes from.
+--
+--   <mame> vt1200 -rompath harness/mame/roms -video none -sound none -nothrottle \
+--       -debug -debugger none -autoboot_script harness/mame/stackwalk.lua -autoboot_delay 0
+--
+-- TMS34010 note: SP is a *bit* address, and a 32-bit word occupies 32 bit
+-- addresses, so consecutive stack words are +/- 32.
+
+local function hex(v) return string.format("%08X", v) end
+
+local machine = manager.machine
+local cpu = machine.devices[':maincpu']
+local dbg = machine.debugger
+local prog = cpu.spaces['program']
+local pc = cpu.state['PC']
+local sp = cpu.state['SP']
+
+if not prog or not prog.read_u32 then
+	print("ERROR: program space has no read_u32")
+end
+
+local TARGET = tonumber(os.getenv("WALK_PC") or "0x3FDCE400")
+local SKIP = tonumber(os.getenv("WALK_SKIP") or "40")
+local frames = 0
+local done = false
+
+emu.register_frame_done(function()
+	frames = frames + 1
+	if done then return end
+	if pc.value == TARGET and frames > SKIP then
+		done = true
+		local s = sp.value
+		print(string.format("=== parked at %s  SP=%s  frame=%d ===", hex(TARGET), hex(s), frames))
+		for i = -4, 28 do
+			local a = (s + i * 32) & 0xFFFFFFFF
+			local v = prog:read_u32(a)
+			local tag = ""
+			if v >= 0x3F200000 and v < 0x40000000 then
+				tag = string.format("   <- ROM bit addr -> file 0x%06X", (v - 0x3F200000) / 8)
+			elseif v < 0x00200000 then
+				tag = "   <- low RAM bit addr"
+			end
+			print(string.format("  [%+3d] @%s = %s%s", i, hex(a), hex(v), tag))
+		end
+		machine:exit()
+	end
+end, "vt1200-stackwalk")
+
+dbg.visible_cpu = cpu
+dbg.execution_state = 'run'