pull-ups 12c509

mmanisse · Joined: 08 Apr 2005 Posts: 1

Hi
I'm using for the first time the 12c509 with pcw compiler 3.15
How can I manage the pull-ups on this chip.
On help there is write that the port_b_pull_up command is available only for 16 & 14 bit micro.

How can I use this function on this pic?

Tnx
Mario Embarassed

dyeatman · Joined: 06 Sep 2003 Posts: 1923 Location: Norman, OK

If you look at the datasheet, the OPTION register bit 6 enables/disables the GP0,GP1/GP3 pullups.

Load the W register with your desired bit configuration for the OPTION register then use the assembly OPTION instruction to transfer it to the OPTION register similar to the following:

#asm
movlw 0x40
OPTION
#endasm

BTW< beware that other instructions that use the OPTION register will overwrite the OPTION register, so you will need to set all the bits at one time manually. For example a setup_timer() command will overwrite the OPTION bits. So use the datasheet,plan ahead and set them all with one command.