Hi, All, I'm disassembling a vintage program and ran across this bit of code that is causing emulators to hang...
MYSUB: LD A,R JP M, MYSUB JR Z, MYSUB CP 0x65 RET M LD A, 0x32 RET I know plenty of 8-bit assembler (mostly 6502, 1802, and a couple others), but I'm by no means expert on the Z-80. It appears that this subroutine is spinning on the value of the refresh register if it's zero or negative, then if it's below 0x65, return the former contents of the refresh register and if not, return 0x32? If it helps, this is from a CP/M game. I'm wondering if this is some sort of randomizer or delay routine. So far, this loop hangs on all three emulators I've tried - simh's altairz80, simcpm010 for AmigaDOS, and EMUZ80 for Raspberry Pi. I'm guessing none of these environments emulate specific behavior of the Refresh register? Does anyone have any comments or insights about what this is really doing and what the right thing to do for emulators is? I can patch this if that's what's needed, but I'd like to understand it first. Thanks, -ethan
