Need urgent help with PIC to PIC communication

[aamiralikhoja]

Need urgent help

I am using pic16f877A microcomputer in same circuit board pin 33 of PIC16F877A (configured as input) is connected with pin 13 of 89c51 (configured as output ) . pin no 13 of at89c51 microcontroller is connected with intr of pic 16f877a pin 33. when logic 1 is applied to 877a voltage on pin is 5 V but when logic 0 is applied, voltage is somewhere between 1.2v to 1.4 volts therefore some times 877a does not recognize interrupt.

 

[cameo_2007]

Need urgent help

for a testing, just disconnect pin33 of 877a from pin13 of 89c51.
now just see the voltage levels.. both high and low.
is it behaving the same manner?

 

[erio]

Re: Need urgent help

Maybe u need a pulldown resistor..im not sure,please post schematic and code for us to troubleshoot..

 

[naveshece]

Re: Need urgent help

hi,
These problems occur in microcontrollers. So, as erio told better you add one pull down resistor and make your PIC input 0..

 

[dimas_lilik]

Need urgent help

Hello
If you use pin 13 of 89c51 (port 3), P3.3 INT1 (external interrupt 1).
The Port 3 output buffers can sink/source four TTL inputs
I think you can use Port 0 to solving problem because Port 0 is an 8-bit open drain bidirectional I/O port. As an
output port each pin can sink eight TTL inputs.