This code may be compiled to 16F84 changing the 12c508.h file
Sorry for the tabs, cut&paste missed it.

BR's
J Souto

/*--------------------------------------------------------------------------+
 | Asynchronous Serial communication routines for 12c508                    |
 | Author: Jose Luiz Pinto Souto                                            |
 | souto@cryogen.com                                                        |
 | 9600 BPS, 1 start bit, 8 data bits, 1 stop bit                           |
 |             |
 | Compiled with CC5xFree from www.bknd.com        |
 +--------------------------------------------------------------------------*/

/*
** 4 MHz Internal Oscillator
*/

#include <12c508.h>

char rxBuf;

#pragma bit RxD_pin @ GP3
#pragma bit _TxOUT  @ GP2


/*
;----------------------------------------------------------------------------*
; GPIO.0 : output - unused
; GPIO.1 : output - unused
; GPIO.2 : output - TxD pin
; GPIO.3 : input  - RxD pin (obs.)
; GPIO.4 : output - unused
; GPIO.5 : output - unused
;----------------------------------------------------------------------------*
  obs.: requires external pull-up or internal week pull-up enabled
*/


/*--------------------------------------------------------------------------*/
void Delay_uSeg (char timeout)
/*--------------------------------------------------------------------------*/
{
    // delay = 3*timeout + 7uS (including call and return)

    while (1) {
        timeout--;
 if (timeout==0) {
     nop();
     nop();
     return;
 }
    }
}

/*--------------------------------------------------------------------------*/
void TxSerial (char txBuf)
/*--------------------------------------------------------------------------*/

/*
 ;---------------------------------------------------------------------------*
 ; Transmit 1 start bit Lo, 8 data bits and 1 stop bit Hi at 9600 bps
 ; No Parity
 ; Byte time = 1.040 mS
 ; Bit  time = 104 uS (0.16% erro w/4.00 Mhz Internal RC)
 ; Input : W = byte to be transmitted
 ; Output: byte transmitted by serial pin
 ;---------------------------------------------------------------------------*
*/

{
    char idx;

    while (1) {
        Carry = 0;   // start bit
        for (idx=10; idx; idx--) { // 3us
            _TxOUT = Carry;  // 4us
            Delay_uSeg(28);  // 91us (28*3+7)
            Carry  = 1;   // 1us
            txBuf  = rr(txBuf);  // 1us
            nop();   // 1us
        }    // 3us
        return;
    }
}

/*--------------------------------------------------------------------------*/
void RxSerial (void)
/*--------------------------------------------------------------------------*/

/*
 ;---------------------------------------------------------------------------*
 ; Receives 1 start bit Lo, 8 data bits and 1 stop bit Hi at 9600 bps
 ; No Parity
 ; Byte time = 1.040 mS
 ; Bit  time = 104 uS (0.16% erro w/4.00 Mhz Internal RC)
 ;
 ; False start bit check
 ;
 ; Start bit hunting timeout = 4*1.283ms
 ;
 ; Input  : none
 ; Output : Carry = 1 => success
 ;      rxBuf = input byte
 ;      Carry = 0 => error (timeout or stop bit=0)
 ;---------------------------------------------------------------------------*
*/

{
    char idx;

    rxBuf = 4;    // 5.135 ms timeout
    idx   = 0;

    while (1) {
        while (RxD_pin) {  // input "high"
            if ((-- idx)==0) {
                if ((-- rxBuf)==0) {
                    Carry = 0;
                    return;
  }
     }
 }

 Delay_uSeg(14);   // 1/2 bit delay (14*3+7)
 if (RxD_pin)
            continue;   // false start bit detection

 rxBuf = 0x80;   // 8 bits counter and reception buffer
        nop();
        nop();    // timming adjustment

 do {
     Delay_uSeg(30);  // (30*3+7)us
     Carry = RxD_pin;  // bit read
     rxBuf = rr(rxBuf);  // store and count
 } while (Carry==0);

        Delay_uSeg(30);   // 1 bit delay
        nop();    // timming adjustment
 Carry = RxD_pin;  // stop bit read
        return;    // 100 us availiable
    }
}

/*--------------------------------------------------------------------------*/
void main( void)
/*--------------------------------------------------------------------------*/
{
    OSCCAL    = W;   // Oscilator Calibration Value
    GPIO      = 0b00011000;
    TRIS      = 0b00001000;
    OPTION    = 0b10000000;  // intenal pull-up enabled

    // Serial routines usage example

    char a;

    a = 0xAA;

    TxSerial(a);
    TxSerial(0x55);

    do {
        RxSerial();
    } while (Carry==0);
    a = rxBuf;

    RxSerial();
    if (Carry==1) {
        a = rxBuf;
    }
}