This has to rate as the most boring question ever asked, but it caused a problem in one of my programs. MPSIM shows the DC (half carry) bit as being set by a CLRW instruction on a 16C54 processor. Is this an MPSIM bug, or does the CLRW really set DC ? It seems really perverse if it does, or alternatively Microchip employ members of the Z80 design team ! Robin +-----------------------------------------------------------------------+ | | | robin.abbott@dial.pipex.com | | | | PIC programmers and BASIC development systems from | | FOREST Electronic Developments. Visit our home page at | | | | http://www.ibmpcug.co.uk/~gmwarner/fed.htm | +-----------------------------------------------------------------------+