Four RS232 ports on PIC

First advice - write down the requirements and THEN choose a microcontroler having all the needed resources onboard. There are plenty of uCs with 4 or 5 UARTS, presumably not more expensive and faster than PIC (like Renesas H8 and M16C families). Why do you make things harder by sticking to the chip which is not suitable for your application?

Having said that, you have at least 2 options if you decide to use that bad PIC ;):

- implement a software UART using timer, interrupts and some fancy code,

- buy an external UART chip with SPI interface (like Maxim MAX3100 if memory serves me right).

Whats possible depends on baudrates, traffic and what else you need to as well. You need to write a spec.

I designed a system like that where I worked some years ago for a comms hub, using four AT90S2313s (they have fast UARTs) connected to a PIC via SPI, using software SPI on the AVRs. The RAM on the AVRs was useful for buffering data. The system worked very well, I think it is still in production.

Leon