BSNES/Lua: Value of V and H registers appear to always be equal.

[aexoden]

Summary

When using the BSNES core (I have not tested others), the values of the V and H scanline registers appear to be identical at all times, as returned by the Lua emu.getregister() function.

Repro

This Lua script can demonstrate the behavior:

local function read_registers()
	pc = emu.getregister("PC")
	v = emu.getregister("V")
	h = emu.getregister("H")
	console.log(string.format("PC:%06X V:%3d H:%3d", pc, v, h))
end

event.onmemoryexecuteany(read_registers)

I have no interest in using onmemoryexecuteany, but event.onmemoryexecute targeted to the code of interest demonstrates the same behavior.

Output

This output was produced by the Lua script (truncated to only a few instructions for demo purposes):

PC:008F13 V:225 H:225
PC:000200 V:225 H:225
PC:009085 V:225 H:225
PC:009086 V:225 H:225
PC:009088 V:225 H:225
PC:009089 V:225 H:225
PC:00908A V:225 H:225
PC:00908B V:225 H:225
PC:00908C V:225 H:225

When doing a trace log of the same frame, the results are as follows:

008f13:  lda  $7d       [00067d]   A:0001 X:0010 Y:0050 S:02f9 D:0600 DB:00 nVMxdIzc V:225 H:  1
000200:  jml  $009085   [009085]   A:0001 X:0010 Y:0050 S:02f5 D:0600 DB:00 nVMxdIzc V:225 H: 22
009085:  php                       A:0001 X:0010 Y:0050 S:02f5 D:0600 DB:00 nVMxdIzc V:225 H: 30
009086:  rep  #$20                 A:0001 X:0010 Y:0050 S:02f4 D:0600 DB:00 nVMxdIzc V:225 H: 36
009088:  pha                       A:0001 X:0010 Y:0050 S:02f4 D:0600 DB:00 nVmxdIzc V:225 H: 41
009089:  phx                       A:0001 X:0010 Y:0050 S:02f2 D:0600 DB:00 nVmxdIzc V:225 H: 49
00908a:  phy                       A:0001 X:0010 Y:0050 S:02f0 D:0600 DB:00 nVmxdIzc V:225 H: 56
00908b:  phb                       A:0001 X:0010 Y:0050 S:02ee D:0600 DB:00 nVmxdIzc V:225 H: 64
00908c:  phd                       A:0001 X:0010 Y:0050 S:02ed D:0600 DB:00 nVmxdIzc V:225 H: 69

I've looked over some of the relevant BizHawk code and I don't see any obvious reason this should be the case, so I'd like to hope I'm simply doing something wrong.

Host env.

• BizHawk 2.3.2; Win10 Pro 1909; Intel/NVIDIA
• BizHawk 2.4.2; Win10 Pro 1909; Intel/NVIDIA

[zeromus]

note, this script is not likely to work the way you want due to the lua console.log being very limited for some reason and certainly not suitable for replicating the tracelog