Problem with interfacing two micros through I/O ports

[ece4afe]

hello,

I have a problem in interfacing two microcontrollers thru their general purpose i/o.
The i/o of each mcu works properly if each was tested individually (w/o connecting them together). But when the two were already connected, we were not able to achieve the expected outcome of the system.

I used a buffer, to ensure the integrity of signal. But, the same situation occured.

For your info, the initial state is zero or low.

What do you think would be the problem? How can I resolve this?

tnx

Chris [/b]

 

[sunking]

i/o port problem

1. does the two port have the matched logic voltage?
2. does the i/o have the right driver ability?

 

[IanP]

Re: i/o port problem

Driving microcontroller pin with another microcontroller pin should not be a problem. In some cases you may need to add a pull-up resistor, but that is all.
In more than 90% of cases problems occure when you try to synchronize data transfer between microcontrollers.
If the signal is one-bit wide, you should use interrupt pins on both microcontrollers; if the signal contains - say - 8-bits, you should dedicate additional bit connected to interrupts of both microcntrollers to inform them that data is ready for transfer and make these interrupts of the highest priority ..
Regards,
IanP

 

[VVV]

Re: i/o port problem

This should be very easy. Therefore I suspect a wrong connection, or wrong pin definition.
I suggest you recheck the connections.
Did you check to make sure the IO points are defined correctly as inputs/ outputs?