That post was in error, but there was no way to change it. You can get up
to 19200 bps with a 4MHz osc with PBP's DEBUG.
Someone mentioned the error, but it wouldn't allow me to change it.
However, you definitely can get up to 115200 bps with a 4MHz osc, but you'll
need to use assembler. Try this;
processor 16F876a
#include <P16F876a.inc>
errorlevel -302 ; suppress "not in bank 0" message
; Defines
#define TxPin PORTC,6 ;define serial TX pin
#define bank1 banksel 0x80 ;select bank 1
#define bank0 banksel 0x00 ;select bank 0
; variable allocations
cblock 0x20 ;start at RAM location 20h
Counter ;bit counter
TxByte ;holds byte to transmit
MsgPtr ;message character pointer offset
CharCnt ;number of characters in text message
dlyLSD ;for delay loop
endc
org 0x00 ;reset vector
goto Main
org 0x05 ;required for MCS loader
Main
call Init ;init port
MsgLoop
movlw .17 ;17 characters in the message
movwf CharCnt ;load character count
movlw .0 ;pointer offset to 1st char in table
movwf MsgPtr ;load character pointer
NextChar
movf MsgPtr,w ;load char pointer into W reg
call Message ;fetch character from table
call TxRoutine ;send it
incf MsgPtr,f ;increment char pointer
decfsz CharCnt,f ;decrement char count, skip if done
goto NextChar ;not finished, then fetch next char
call Delay_50uS ;short delay between messages
goto MsgLoop ;continuous loop
Message ;prints Hello World....!<CR>
addwf PCL,f ;load character offset
retlw 'H' ;return with ASCII character in W reg
retlw 'e'
retlw 'l'
retlw 'l'
retlw 'o'
retlw ' '
retlw 'W'
retlw 'o'
retlw 'r'
retlw 'l'
retlw 'd'
retlw '.'
retlw '.'
retlw '.'
retlw '.'
retlw '!'
retlw '\r' ;carriage return tagged onto end of message
TxRoutine
movwf TxByte ;load byte to send into TxByte
movlw .8 ;preload bit counter with 8
movwf Counter
StartBit
bcf TxPin ;true mode / low for START bit
goto $+.1 ; 2uS
goto $+.1 ; 2uS
nop
TxLoop
rrf TxByte,f ;rotate into carry / send LSB first
btfsc STATUS,C ;if bit = 1 then
goto SetBit ;send a 1
bcf TxPin ;else send a 0
goto $+.1 ;2uS
decfsz Counter,f ;decrement bit count
goto TxLoop ;if not 0, then continue
goto StopBit+.2 ;else send stop bit
SetBit
bsf TxPin ;send 1
nop
decfsz Counter,f
goto TxLoop
StopBit
nop
goto $+.1 ;2uS
goto $+.1 ;2uS
bsf TxPin ;begin stop bit period
goto $+.1 ;2uS
goto $+.1 ;2uS
return ;2uS rest of program handles the rest
Init
bank0
movlw b'01000000' ;TX pin idles high (true mode)
movwf PORTC ;set port latches
bank1 ;bank 1
movlw b'10000000' ;RX in, rest outs
movwf TRISC ;set port directions
bank0 ;back to bank 0
return
Delay_50uS ;call + delay + return = 50uS
movlw .15 ;at 4MHz
movwf dlyLSD
decfsz dlyLSD, f
goto $ - .1
return
end