Hi Stefan,

> I am new to PICs so please excuse any blatant ignorance....  I am trying =
> a simple application for a 12C671 using MPLAB 3.40.  Trouble is I cannot =
> seem to get the I/O's to toggle under the simulator (no change in the =
> gpio SFR) by=20

Not sure what the simulator should be doing here but the hardware will
not work as you have programmed it.

>              movlw   b'00001001'        ;
>              movwf   TRISIO               ; port 0, 3 are inputs, rest =
> outputs

The 12C671 is almost certainly a 12bit core like the 12C508/9 which I have
used.  They do not use the TRISIO register as a regular register.

You have to use the TRIS instruction.  Best you examine the short
one page opcode listing to check which special opcodes are supported
when changing between 12, 14 or 16 bit programming.

Cheers
--
Kalle Pihlajasaari   kalle@ip.co.za   http://www.ip.co.za/ip
Interface Products   P O Box 15775, DOORNFONTEIN, 2028, South Africa
+ 27 (11) 402-7750   Fax: 402-7751    http://www.ip.co.za/people/kalle

DonTronics, Silicon Studio and Wirz Electronics uP Product Dealer