How do I enable a Pull Up

Which chip are you using? Which Assembler are you using? What header files did you include?

Some of the MSP430 chips do not have internal pull-up/down resistors. But the Assembler should have caught that unless you fooled it with a wrong header file.

I am using the IAR assembler that I just updated.

#include  <msp430G2231.h>

The device is MSP430G2231.

Tom

#include <msp430G2231>
   RSEG  CODE
main:
   mov   #5A80h, &WDTCTL
   bic.b #08h, P1DIR
   bis.b #08h, P1REN
   bis.b #08h, P1OUT
forever:
   jmp   forever
   RSEG  RESET
   dw    main
   END

Yes, that is exactly what I have:

bic.b   #08h, &P1DIR            ; Set P1.3 INPUT
bis.b   #08h, &P1REN            ; Pull up on P1.3 input
bis.b   #08h, &P1OUT            ; Enable pull up resistor

bic.b   #0FFh, &P2DIR           ; Set P2 as INPUT Port

The first line in my original post was copied in error. The above is a cut and paste. I do stop the watchdog timer.

I checked with a scope and there is no pull up on the pin. Replaced the device, reprogrammed and checked the pin with a scope probe. Same result. There is no pull up on the pin.

The program runs fine as long as there is an external pull up resistor.

I assume that I am doing it wrong, but I can't figure out how.

Tom

Tom Harper said:

Yes, that is exactly what I have: ...

Really exactly ? Was there a "forever: jmp forever" after those statements? The & in those statements are not that important. But what the CPU does afterwards is important. I suggest you try my code in its entirety and measure the P1.3 with a scope or even a DVM (Digital Volt Meter).