Ash;
I told you it was more complex then first impressions
It's a little difficult to just draw you a design as one could use more details about the application and use. I assume this is for testing and troubleshooting the design and not required for the final product?
If it's just for testing then you need to define if you can utilize a PC with two comm ports or can you have two PC systems available for the testing period? Having two PC would make the testing session a little more straight forward as you won't have to figure out which instance of hyper terminal is active and which COMM port is monitoring which of the two PIC data lines.
If you have only one PC with one COMM port then you have the problem of output data from the PC. How will you determine which PIC signal input will receive the data from the PC, #1 pic, #2 pic or both at the same time without some kind of manual switching function?
Also can the two PICs be sending data to each other at the same time or will data only be sent in one direction at any specific time (half-duplex or full duplex)? If full duplex then you will defenitly need two COMM ports or two computers to do the monitoring as ORing two PIC data streams with one COMM input port will garble data if the two PICs send data at the same time.
The ORing logic needs to be performed on the TTL side of the max232converter(s) of course. If I recall the RS-232/TTL converters utilize a negative logic such that when no data is being send (steady mark condition) the TTL level is at a high state. If that is fact then the ORing function can be performed using a 2 input AND gate (74LS08 should work). If the serial logic level is using positive logic (steady mark condition = TTL high state) then a 74LS32 OR gate would perform the proper function. Each 74LS08 (or 32) has four gate functions avalible.
This ORing function gate would be used where ever you want to have two TTL output pins sending to one TTL input pin. How many Oring function you need again depends on the number of COMM ports or computers you have avalible for testing.
Lefty