Interconnected chips and pin settings

[mackrackit]

What voltage are you running the PIC at and what is the max voltage of the other chip? The max voltage it can handle?

[bluesmoke]

I am running both the 16f887 and umFPU at 3.3V.

umFPU can run at up to 5V.

[comwarrior]

can you not put resisters between the pic and the mathco? that should stop the mathcpu from grounding sending a pic output line to ground and poping the chip...

But yes, the startup of the chip needs to send all outputs low and then set the relivant lines to inputs right at the beginning...

So...

TRISE = %00000111
TRISD = %00000000
TRISC = %00000000
TRISB = %00000000
TRISA = %11111111
PORTA = 0
PORTB = 0
PORTC = 0
PORTD = 0
PORTE = 0

Setting TRIS to 1 makes that bit an input...
the PORT commands makes all the ports low...

I hope that helps

[bluesmoke]

Thanks Comwarrior, I think that resistors between the two processors is what was needed.