Communication between 2 microcontrollers

[c0de]

Is it possible to control 2 serial lines with a pic16f876? (one serial for PC and one serial for another pic16f876) ... or in other words, to have multiple Rx/Tx pins.

I would like to have something like this:


PIC1 <----Rx/Tx----> PIC2 <----Rx/Tx----> Computer

I wonder if it's possible to have for PIC2, two rs232 line... like:
#use rs232(baud=9600, bits=8, parity=N, xmit=PIN_C6, rcv=PIN_C7,stream=Computer)
#use rs232(baud=9600, bits=8, parity=N, xmit=PIN_B1, rcv=PIN_B2, stream=PIC1)

... and control the PC and PIC1 streams.

P.S: if it's possible, do I need something (like max232) between the RX/Tx lines of the two PICs or is enough to connect PIC1(Tx) - PIC2(Rx), PIC1(Rx)-PIC2(Tx) directly.

Thank you.

[Ttelmah]

Yes, you can control two serial lines. The 'second' serial (not using the hardware pins), will be implemented as a 'software' serial link.
Problems of this, are that there is no buffering in either direction, so a chip 'receiving' on such a link, _must_ poll the receive line (kbhit), at least once every half bit time, to have any hope of spotting a character arriving, and that communications in both directions, can/will be damaged, if the processor is asked to do anything else (service interrupts...), while the data is being sent/received.
In general, if one chip is talking to the PC using it's hardware UART, and then acts a 'master' device, talking to the other PIC, and initiating all transfers, with the second PIC, using it's hardware port, this can be made to work.
No, you don't need MAX232 type buffers, provided the connection is reasonably short.
Worth asking though, if you could use the second hardware serial that is present?. As well as the normal asynch serial, there is a synchronous interface, that handles SPI, and I2C connections, and this has full buffering and hardware present, to do the transfers. Much faster, and more reliable than software asynch, if the hardware is not being used for anything else...

Best Wishes

[rnielsen]

Microchip does make several PIC's that have two UARTs. Take a look and see if one of these might meet your requirements.