> > I'd suggest finding a VHDL or Verilog implementation, and see if > > that provides any insight. The MAME 6800 core says it is illegal. Which mean the opcode is just skipped. <http://messdev.fdns.net:6502/cgi-bin/viewcvs.cgi/src/cpu/m6800/6800ops. c?rev=HEAD&content-type=text/vnd.viewcvs-markup> -- tim lindner tlindner at ix.netcom.com Bright