-- frame_clock.lua -- read-only frame counter side channel for host-driven tests.
--
-- Writes the current frame number to $FRAME_CLOCK once per frame so a host
-- client can align an injection with a known emulated frame (and therefore with
-- the driver's VT1200_DUMP_FRAMES schedule).  No breakpoints, no memory writes
-- except this file.  Optionally exits at $FRAME_STOP.
local machine = manager.machine
local path = os.getenv("FRAME_CLOCK")
local stop = tonumber(os.getenv("FRAME_STOP") or "0")
local f = 0

emu.register_frame_done(function()
	f = f + 1
	if path then
		local fh = io.open(path, "w")
		if fh then
			fh:write(string.format("%d\n", f))
			fh:close()
		end
	end
	if stop > 0 and f >= stop then
		print(string.format("frame_clock: stopping at frame %d", f))
		machine:exit()
	end
end, "vt1200-frame-clock")