LIST P = 16F84A ; 115200 full duplex (send delayed up to 8us) ; 115200 = ; 20 MHz = .2 us/instruction ; INCLUDE __CONFIG _PWRTE_OFF & _HS_OSC & _WDT_OFF ; configuration switches ; SP equ 0 ;Send Pin GP equ 1 ;Get Pin AD2 equ 2 ;a2 pin AD3 equ 3 ;a3 pin Reg B = a1 a0 d5 d4 d3 d2 d1 d0 AMSK equ 0xf3 ;mask for AD2 AD3 (0xf3 for pins 2 and 3) EIO equ 4 ;Enable IO 4-16 GR equ 0xc ;byte to get SR equ 0xd ;byte to send GF equ 0xe ;get flag SF equ 0xf ;send flag GK equ 0x10 ;get count SK equ 0x11 ;send count TGR equ 0x12 ;temp Get Register GR2 equ 0x13 ;Get Register for byte 2 DEL equ 0x14 ;delay count TST equ 0x15 ; ORG 0 ; bsf STATUS,RP0 ;select reg bank 1 movlw 0x2 movwf TRISA ;set port A pin 0 as out, pin 1 as in movlw 0x0 movwf TRISB ;set PORTB to output bcf STATUS,RP0 ;select reg bank 0 bsf PORTA,SP ;set send pin ; ; clrf GR clrf GR2 clrf SR clrf GF clrf SF movlw 0x30 movwf SR ;bsf SF,0 movlw 0xa movwf SK movlw 0x9 movwf GK TOP btfss GF,0 goto I1GA1 ;check for start bit decfsz GK,1 goto I2GA1 ;get bit movlw 9 ;stop bit - no need to get movwf GK movlw AMSK ;12 2 bcf cause problems andwf PORTA,1 ;13 set a3 a2 btfsc GR,0 bsf PORTA,AD2 btfsc GR,1 bsf PORTA,AD3 clrf GF ;13 goto TOP2 ;15 ;later finish send stop bit ;the main idea is that TOP2 will land early on the stop bit ;the stop bit is 1 and the program will have time to get the ;next start bit (0) NEXT btfss SF,0 goto I1S btfsc SF,1 goto I2S ;send start bit decfsz SK,1 goto I3S ;send data bit goto I4S ;send stop bit I3S movf PORTA,0 ;8 btfsc SR,0 iorlw 0x1 btfss SR,0 andlw 0xfe movwf PORTA ;13 * nop rrf SR,1 ;15 ;14+15+14=3.0+2.8+2.8=8.6 us (8.6806 us) LAST btfss GF,1 goto I1GB1 ;check for start bit decfsz GK,1 goto I2GB1 ;get bit movlw 9 ;stop bit - no need to get movwf GK movlw AMSK ;12 2 bcf cause problems andwf PORTA,1 ;13 set a3 a2 btfsc GR,0 bsf PORTA,AD2 btfsc GR,1 bsf PORTA,AD3 clrf GF goto TOP2 ;goto TOP2 ;15 (14+14=28 early 5.6 us) TOP2 btfss GF,0 goto I1GA2 ;check for start bit decfsz GK,1 goto I2GA2 ;get bit movlw 9 ;stop bit - no need to get movwf GK movf GR2,0 ;set b7-b0 (a1 a0 d5 d4 d3 d2 d1 d0) movwf PORTB ; movlw 0x3e ;test ; movwf GR2 ;test movlw 3 movwf SF ;set send flag bcf GF,0 ;11 ;nop ;12 get in inst part goto INST ;13 goto INST? (16+15=31 extra 6us) LAST2 btfss GF,1 goto I1GB2 ;check for start bit decfsz GK,1 goto I2GB2 ;get bit movlw 9 ;stop bit - no need to get movwf GK movf GR2,0 ;set b7-b0 (a1 a0 d5 d4 d3 d2 d1 d0) movwf PORTB ; movlw 0x55 ;test this part (has error) ; movwf GR2 ;test movlw 3 movwf SF ;set send flag clrf GF ;11 ; nop ;12 get in inst part goto INST ;13 (16+15= 31) NEXT2 nop ;1 delay for 1/3 cycle nop nop nop nop nop nop nop nop nop nop nop nop goto TOP2 ;15 ;no send while getting byte 2 ;use time to process PIC instructions for external devices (inputs, motors, ...) ;already set a3 a2 ; and a1 a0 b5-b0 INST btfss GR,2 ;1=get input goto I1I bsf STATUS,RP0 ;select reg bank 1 movlw 0x3f movwf TRISB ;set PORTB to ooiiiiii bcf STATUS,RP0 ;select reg bank 0 ;the 4-16 address and data lines are set ;this will send the PIC the (input) instruction bsf PORTA,EIO ;enable 4-16 ;nop ;extra inst bcf PORTA,EIO ;disable 4-16 movf PORTB,0 ;copy PORTB to Send Register ;movlw 0x1e ;test value in SR ;btfsc TST,7 ;for test ;movf GR2,0 ;GR ;btfss TST,7 ;for test ;movf GR2,0 ;test byte2 ; movf GR,0 ;test byte2 movwf SR bsf STATUS,RP0 ;select reg bank 1 clrf TRISB ;set PORTB back to oooooooo bcf STATUS,RP0 ;select reg bank 0 goto NEXT ;1st do any sendTOP ;15 go back to getting byte 1 ;---end main loop I1GA1 btfsc GF,1 ;4 check for start bit goto I3GA1 ; nop ; btfsc GF,2 btfss PORTA,GP ;7 * start bit = 0 bsf GF,0 ;got sb, get sb next cycle nop ; goto I4GA1 nop ;Did not get start bit delay nop nop ;12 nop goto NEXT ;15 I2GA1 rrf GR,1 ;6 get bit movf PORTA,0 ;7 * movwf TGR ;8 btfsc TGR,GP ;9 bsf GR,7 ;10 btfss TGR,GP ;11 bcf GR,7 ;12 nop goto NEXT ;15 I3GA1 nop ;7 getting byte in other part nop nop nop nop nop nop goto NEXT ;15 I1S nop ;4 nop nop nop nop nop nop ;10 nop nop nop goto LAST ;15 I2S nop ;6 send start bit nop nop decfsz SK,1 bcf SF,1 ;clear bit 1 = do not send start bit again nop nop bcf PORTA,SP ;13 * goto LAST ;15 I4S movlw 0xa ;9 movwf SK clrf SF ;9 inst 43 inst is most close nop bsf PORTA,SP ;13 * goto LAST ;15 I1GB1 btfsc GF,0 ;4 goto I3GB1 ; nop ; btfsc GF,2 btfss PORTA,GP ;7 * start bit = 0 bsf GF,1 ;got sb, get sb next cycle nop ; goto I4GB1 nop ;Did not get start bit delay nop nop ;12 goto TOP ;14 I2GB1 rrf GR,1 ;6 movf PORTA,0 ;7 * movwf TGR ;8 btfsc TGR,GP ;9 bsf GR,7 ;10 btfss TGR,GP ;11 bcf GR,7 ;12 goto TOP ;14 I3GB1 nop ;7 getting byte in other part nop ; nop ; nop nop nop goto TOP ;14 ;byte 1 above, byte 2 below I1GA2 btfsc GF,1 ;4 check for start bit goto I3GA2 ; nop ; btfsc GF,2 btfss PORTA,GP ;7 * start bit = 0 bsf GF,0 ;got start bit nop ; goto I4GA2 nop ; nop nop ;12 nop goto LAST2 ;15 I2GA2 rrf GR2,1 ;6 get bit movf PORTA,0 ;7 * movwf TGR ;8 btfsc TGR,GP ;9 bsf GR2,7 ;10 btfss TGR,GP ;11 bcf GR2,7 ;12 nop goto LAST2 ;15 I3GA2 nop ;7 getting byte in other part nop nop nop nop nop nop goto LAST2 ;15 I1GB2 btfsc GF,0 ;4 goto I3GB2 ; nop ; btfsc GF,2 btfss PORTA,GP ;7 * start bit = 0 bsf GF,1 ;got start bit nop ; goto I4GB2 nop ; bsf GF,2 ;got sb, get sb next cycle nop ;Did not get start bit delay nop nop ;12 goto NEXT2 ;14 I2GB2 rrf GR2,1 ;6 movf PORTA,0 ;7 * movwf TGR ;8 btfsc TGR,GP ;9 bsf GR2,7 ;10 btfss TGR,GP ;11 bcf GR2,7 ;12 goto NEXT2 ;14 I3GB2 nop ;7 getting byte in other part nop nop nop nop nop goto NEXT2 ;14 I1I nop ;4 output only nop nop nop ;7 nop nop nop ;10 ;the 4-16 address and data lines are set ;this will send the output instruction bsf PORTA,EIO ;11 enable 4-16 bcf PORTA,EIO ;12 disable 4-16 clrf SF ;13 clear Send Flag set in past to save time goto TOP ;15 go back to getting byte 1 no need to send first Delay decfsz DEL,1 ;DEL*3+5 DEL>0 goto Delay ;1=8,2=11,3=14,4=17,5=20,6=23 return ;7=26,8=29,9=32,10=35 END