Post by thread:RTCC as INPUT (II)

PICers, Ha - it works! This is the sorta thing that makes you look like a real schmutz. OBVIOUSLY, you've gotta configure TMR0 separately and then test for an increment. I was doing config & inc test in the same sub-routine, which means you'd have to be lucky for your rising edge to rise in the few u-secs between configuring and testing. Well, figured that one out for myself ... ;********************************************************************** ;PROBLEM : Use RTCC to detect presence of a data pulse and then grab the data nibble in ;PORTA and store it. ; ;TMRset configures RTCC to increment on the rising edge of an input ;pulse applied to the TMR0 pin. Used to detect the presence of data. ;********************************************************************** TMRset clrf TMR0 ;Clear TMR0, 0x001 nop movlw B'11101000' OPTION ;Configure the PRESCALER nop retlw 0x00 ;********************************************************************* ;FETCH - monitors the VT pin on the 74C922, grabs the data nibble and ;stores it in KeyData. It then sets b3 in flags before returning. ;This routine uses the transits on TOCK1 to determine if an input is ;present. RTCC=TOCK1 in the newer PIC 16C5* series. ;OPTION.3=1 .. prescaler assigned to the WDT ;OPTION.4=0 .. increment on L->H transit on TOCK1 ;OPTION.5=1 .. transition on TOCK1 pin ;OPTION.0,1,2=0 .. ;Restore the default OPTION setting before we leave? ;Clear VT in the MAIN PROGRAMME, NOT in this subroutine. ;******************************************************************* fetch btfss TMR0,0 ;Has TMR0 been incremented? goto $+4 ;No - exit the subroutine. movf PORTA,0 ;Yes - there are data present. movwf KeyData ;Store the data bsf flags,VT ;Tell the main programme nop ;Jump to here if no input clrf TMR0 ;And clear TMR0 before leaving retlw 0x00