Post by thread:PIC16c74

Hi, I'm using the code below to receive a byte from the US ART. When I get the byte I display it on the LED's and echo it back. This code is not working for me. Can anybody tell me what I'm doing wrong. Thanks list p=16c74 Title "first aidi Program" include <P16C74.INC> org 00h Start clrf PORTB ;Clear PORT_B output latches bsf STATUS,RP0 ;Go to Bank1 clrf TRISB ;Config PORT_B as all outputs movlw 19h ;Set Band rate (9600 baud @4MHz) movwf SPBRG movlw b'00100100' ;8-bit transmit, transmitter enable movwf TXSTA ;Asynchronous mode, High baud rate bcf STATUS,RP0 ;Go to Bank0 movlw b'10010000' ;8-bit receive, receiver enabled movwf RCSTA ;serial port enabled movf RCREG,W ;Get input data movwf PORTB ;Display on LEDs movwf TXREG ;Echo character back goto Start end Aidi Moubhij spam_OUTaidiTakeThisOuTmjr.com

Hi Aidi, Just a couple of things, you should set CREN before clearing SREN, I also found that toggling CREN after receive to clear any rx errors. See code below. You also must wait for the byte to actually be received. {Quote hidden}> Hi, > >I'm using the code below to receive a byte from the US ART. When I get the >byte I display it on the LED's and echo it back. >This code is not working for me. Can anybody tell me what I'm doing wrong. > Thanks > > > list p=16c74 > Title "first aidi Program" > > include <P16C74.INC> > > org 00h > >Start > clrf PORTB ;Clear PORT_B output latches > > bsf STATUS,RP0 ;Go to Bank1 > > clrf TRISB ;Config PORT_B as all outputs > > > movlw 19h ;Set Band rate (9600 baud @4MHz) > movwf SPBRG > movlw b'00100100' ;8-bit transmit, transmitter enable > movwf TXSTA ;Asynchronous mode, High baud rate > > bcf STATUS,RP0 ;Go to Bank0 > > movlw b'10010000' ;8-bit receive, receiver enabled > movwf RCSTA ;serial port enabled > ; ADDED THE FOLLOWING LINES *****; ; RxTest ; ; BSF RCSTA,4 ;set CREN BCF RCSTA,5 ;clear SREN ; RxWait ; BTFSS PIR1,5 ;RxBuffer Full when PIR,5=1 GOTO RxWait ; ; BCF RCSTA,4 ;toggle CREN to clear any Rx BSF RCSTA,4 ;errors. You could choose to ;handle Rx errors differently ;for a "real" application. ; *******************************; {Quote hidden}> movf RCREG,W ;Get input data > movwf PORTB ;Display on LEDs > movwf TXREG ;Echo character back > goto RxTest ; ***Changed here also. > > end >Aidi Moubhij > >.....aidiKILLspam@spam@mjr.com Hope that helps. Ray Gardiner rayKILLspamhdc.com.au

Hi Ray, Thank you very much for your help. What you suggested fixed the problem. Now I can move on to the next step. Thank you again. At 01:08 PM 5/4/99 -0400, you wrote: {Quote hidden}>Hi Aidi, >Just a couple of things, you should set CREN before clearing SREN, >I also found that toggling CREN after receive to clear any rx errors. >See code below. You also must wait for the byte to actually be received. > > >> Hi, >> >>I'm using the code below to receive a byte from the US ART. When I get the >>byte I display it on the LED's and echo it back. >>This code is not working for me. Can anybody tell me what I'm doing wrong. >> Thanks >> >> >> list p=16c74 >> Title "first aidi Program" >> >> include <P16C74.INC> >> >> org 00h >> >>Start >> clrf PORTB ;Clear PORT_B output latches >> >> bsf STATUS,RP0 ;Go to Bank1 >> >> clrf TRISB ;Config PORT_B as all outputs >> >> >> movlw 19h ;Set Band rate (9600 baud @4MHz) >> movwf SPBRG >> movlw b'00100100' ;8-bit transmit, transmitter enable >> movwf TXSTA ;Asynchronous mode, High baud rate >> >> bcf STATUS,RP0 ;Go to Bank0 >> >> movlw b'10010000' ;8-bit receive, receiver enabled >> movwf RCSTA ;serial port enabled >> > >; ADDED THE FOLLOWING LINES *****; > ; >RxTest ; > ; > BSF RCSTA,4 ;set CREN > BCF RCSTA,5 ;clear SREN > ; >RxWait ; > BTFSS PIR1,5 ;RxBuffer Full when PIR,5=1 > GOTO RxWait ; > ; > BCF RCSTA,4 ;toggle CREN to clear any Rx > BSF RCSTA,4 ;errors. You could choose to > ;handle Rx errors differently > ;for a "real" application. >; *******************************; > >> movf RCREG,W ;Get input data >> movwf PORTB ;Display on LEDs >> movwf TXREG ;Echo character back > >> goto RxTest ; ***Changed here also. >> >> end > >>Aidi Moubhij >> >>.....aidiKILLspam.....mjr.com > >Hope that helps. > > > >Ray Gardiner EraseMErayspam_OUTTakeThisOuThdc.com.au > Aidi Moubhij aidispam_OUTmjr.com

Aidi, SREN is not relevant in the Asynchronous mode so there is no need to clear it. What probably fixed your problem is the clearing and setting of the CREN bit which clears the Overrun Error bit, OERR. A better way to handle this is to monitor OERR and FERR (Framing Error). If OERR is set, clear the error by clearing and setting the CREN bit. If FERR is set, clear the error by reading another Byte from the RCREG. While I normally use Parallax/CVASM syntax I can provide a MPASM example if someone else does'nt jump in. This leads to a more serious problem. The 16C74 and 16C74A have a known, documented, bug when using the high-speed mode (BRGH=1). You simply can not get reliable operation with these devices (and the 16C73/73A) when BRGH=1. The simple and low cost solution is to use another crystal. With an 8MHz crystal you can get 9600 +/- 0.16% with BRGH=0 and SPBRG=12. You can also switch to a 16C74B or a 16C77 which work fine with BRGH=1. They are both pin-compatible with the 16C77 having 8K of program memory and 368 Bytes of data memory compared with 4K/192 Bytes for the 16C74x. Another nice thing about the 16C77 is that the upper 16 Bytes of data memory are mapped into all four banks. - Tom At 02:24 PM 5/4/99 -0400, Aidi Moubhij wrote: {Quote hidden}>Hi Ray, >Thank you very much for your help. What you suggested fixed the problem. >Now I can move on to the next step. Thank you again. > >At 01:08 PM 5/4/99 -0400, Ray Gardiner wrote: >>Hi Aidi, >>Just a couple of things, you should set CREN before clearing SREN, >>I also found that toggling CREN after receive to clear any rx errors. >>See code below. You also must wait for the byte to actually be received. >> >>> Hi, >>> >>>I'm using the code below to receive a byte from the US ART. When I get the >>>byte I display it on the LED's and echo it back. >>>This code is not working for me. Can anybody tell me what I'm doing wrong. >>> Thanks >>> >>> list p=16c74 >>> Title "first aidi Program" >>> >>> include <P16C74.INC> >>> >>> org 00h >>> >>>Start >>> clrf PORTB ;Clear PORT_B output latches >>> >>> bsf STATUS,RP0 ;Go to Bank1 >>> >>> clrf TRISB ;Config PORT_B as all outputs >>> >>> >>> movlw 19h ;Set Band rate (9600 baud @4MHz) >>> movwf SPBRG >>> movlw b'00100100' ;8-bit transmit, transmitter enable >>> movwf TXSTA ;Asynchronous mode, High baud rate >>> >>> bcf STATUS,RP0 ;Go to Bank0 >>> >>> movlw b'10010000' ;8-bit receive, receiver enabled >>> movwf RCSTA ;serial port enabled >>> >> >>; ADDED THE FOLLOWING LINES *****; >> ; >>RxTest ; >> ; >> BSF RCSTA,4 ;set CREN >> BCF RCSTA,5 ;clear SREN >> ; >>RxWait ; >> BTFSS PIR1,5 ;RxBuffer Full when PIR,5=1 >> GOTO RxWait ; >> ; >> BCF RCSTA,4 ;toggle CREN to clear any Rx >> BSF RCSTA,4 ;errors. You could choose to >> ;handle Rx errors differently >> ;for a "real" application. >>; *******************************; >> >>> movf RCREG,W ;Get input data >>> movwf PORTB ;Display on LEDs >>> movwf TXREG ;Echo character back >> >>> goto RxTest ; ***Changed here also. >>> >>> end >> >>>Aidi Moubhij >>Ray Gardiner @spam@rayKILLspamhdc.com.au >Aidi Moubhij