PORTB.4 and PORTB.5 conflict

[jerryd]

Electro Tech forum,

Thanks to help I've gotten on this forum I now have change-
state interrupts working on my 16f88. I started out using
PORTB.4 with a 10K pullup. Worked fine.

Since I need 2 change-state interrupts I tried using PORTB.5
along with PORTB.4 but when I put a pullup on PORTB.5,
PORTB.4 no longer causes an interrupt.

PORTB 5, 6 & 7 all work together or separately but PORTB.4
will not work if there is a pullup on PORTB.5.

I've tried 2 different 16f88's with the same results.

I couldn't find anything about this in the datasheet so
there must be something I don't know about this hardware.

I'm OK using RB5 and RB6 for now but I would like to
know what's going on for future use.

Here's my PORTB configuration code when using PORTB<7:4>

'configure port b for hardware spi and hardware interupts
TRISB = %11110001 'portb 0,4,5,6,7 are input
SSPCON = %00100000 'Synchronous Serial Port Enable bit
INTCON = %10010000 'Enable external interrupts
OPTION_REG = %10000000 'Turn off pull-up resistors, falling edge on RB0

Thanks for any reply,
jerryd

 

[Pommie]

You are enabling the serial port and so that will take over some of the pins.

Edit, also, why aren't you using the internal pullups?

Mike.

 

[jerryd]

Thanks Pommie.

Serial mode off, internal pullups on and everything works.

This is what I get for using code off the internet when
I don't understand the hardware.

jerryd

 

[Pommie]

Sounds like your understanding is growing rapidly.

Mike.