Post by thread:16c74 serial routine

Hi all, I have been working on a serial routine using the USART on the 16C74. My question is why doesn't it work on MPSIM? I have checked it out several times using the data sheet for 16CXX series. At first I can see PIR1 <4> is clear when I load the tx data, but when it becomes set I don't get an interrupt! Also I never see the tx pin on portc move. Do I have to initiate anything else for my program to work? See below for program and the response from MPSIM. ;***************************************** ; serial routine for 16C74 (18/02/97) ;***************************************** #INCLUDE <16CXX.INC> TEMP EQU 0X10H ;TEMP STORAGE ORG 0X00H GOTO MAIN ORG 0X04H GOTO INTERUPT MAIN: CLRF TEMP ;CLEAR THE STORAGE MOVLW B'00000000' ;SET PORTC AS ALL OUTPUTS TRIS PORTC ; '' CLRF PORTC ;CLEAR THE PORT bsf STATUS,rp0 ;switch to bank one BSF INTCON,GIE ;ENABLE INTERUPTS movlw .129 ; set up baud rate (9600 @ 20Mhz) movwf spbrg ; '' bsf txsta,brgh ; high baud bcf txsta,sync ;enable port bcf status,rp0 bsf rcsta,spen ; '' bsf status,rp0 ;bank1 bsf pie1,txie ;enable int bcf txsta,tx9 ;disable 9 bit bsf txsta,txen ;enable transmission bcf status,rp0 ;bank0 MOVFW TEMP ;GET TEMP VALUE INTO W MOVWF TXREG ;SEND TO THE TRANSMIT REG ENDLESS_LOOP: NOP GOTO ENDLESS_LOOP INTERUPT: INCF TEMP,F MOVFW TEMP ;data to be transmitted movwf txreg ;transmit RETFIE ;RETURN Here is the response I get from MPSIM: SERIAL RADIX=X MPSIM 5.00 D 16c74 TIME=671502.00u 223945?=Help ---------------------------------------------------------------------------- ---- PORTC: 00000000 TXREG: 00000000 TRISC: 00000000 TXSTA: 00100100 PIR1: 00010000 PIE1: 00010000 RCSTA: 10000000 SPBRG: 10000001 PORTA: 0001000 PORTB: 11111111 PORTD: 11111111 PORTE: 00000000 W: 00000000 TEMP: 00000000 INTCON: 10000000 ---------------------------------------------------------------------------- ---- Interrupt at address 16 0017 2816 GOTO ENDLESS_LOOP % LO C:\PICDE\HNC\SERIAL Hex Code loaded Listing File Loaded Symbol table loaded 277488 bytes memory free % RS Processor Reset % GO Interrupt at address 18 0019 2818 GOTO ENDLESS_LOOP % AD INTCON,B,8 % C Interrupt at address 18 0019 2818 GOTO ENDLESS_LOOP % Many thanks for any input (good or bad), Brian.

Brian, I noticed the same problem on MPLAB's Simulator when I was doing C73A Serial communication. And, along with this, the Simulator will not receive incoming Stimulus file data. I guess the Simulator core that is used, won't simulate the SCI module. To debug my code, I ended up writing a small program (similar to yours below) and debugged it by observing how it worked. Fortunately, this wasn't a big job and the hardware works exactly as advertised in the Datasheets. Good luck, myke {Quote hidden}>Hi all, > I have been working on a serial routine using the USART on the 16C74. > My question is why doesn't it work on MPSIM? > >I have checked it out several times using the data sheet for 16CXX series. > At first I can see PIR1 <4> is clear when I load the tx data, but when it >becomes set I don't get an interrupt! Also I never see the tx pin on portc >move. Do I have to initiate anything else for my program to work? See >below for program and the response from MPSIM. > >;***************************************** >; serial routine for 16C74 (18/02/97) >;***************************************** > >#INCLUDE <16CXX.INC> > >TEMP EQU 0X10H ;TEMP STORAGE > > > >ORG 0X00H >GOTO MAIN > > >ORG 0X04H >GOTO INTERUPT > > > >MAIN: >CLRF TEMP ;CLEAR THE STORAGE > >MOVLW B'00000000' ;SET PORTC AS ALL OUTPUTS >TRIS PORTC ; '' >CLRF PORTC ;CLEAR THE PORT > > > >bsf STATUS,rp0 ;switch to bank one >BSF INTCON,GIE ;ENABLE INTERUPTS > > movlw .129 ; set up baud rate (9600 @ 20Mhz) > movwf spbrg ; '' >bsf txsta,brgh ; high baud >bcf txsta,sync ;enable port >bcf status,rp0 >bsf rcsta,spen ; '' > >bsf status,rp0 ;bank1 >bsf pie1,txie ;enable int >bcf txsta,tx9 ;disable 9 bit >bsf txsta,txen ;enable transmission >bcf status,rp0 ;bank0 > >MOVFW TEMP ;GET TEMP VALUE INTO W >MOVWF TXREG ;SEND TO THE TRANSMIT REG > > > >ENDLESS_LOOP: > NOP > GOTO ENDLESS_LOOP > > > > >INTERUPT: >INCF TEMP,F >MOVFW TEMP ;data to be transmitted >movwf txreg ;transmit >RETFIE ;RETURN > > > > >Here is the response I get from MPSIM: > > > >SERIAL RADIX=X MPSIM 5.00 D 16c74 TIME=671502.00u >223945?=Help > ---------------------------------------------------------------------------- > ---- >PORTC: 00000000 TXREG: 00000000 TRISC: 00000000 TXSTA: 00100100 >PIR1: 00010000 PIE1: 00010000 RCSTA: 10000000 SPBRG: 10000001 PORTA: >0001000 >PORTB: 11111111 PORTD: 11111111 PORTE: 00000000 W: 00000000 TEMP: >00000000 >INTCON: 10000000 > > ---------------------------------------------------------------------------- > ---- >Interrupt at address 16 >0017 2816 GOTO ENDLESS_LOOP >% LO C:\PICDE\HNC\SERIAL >Hex Code loaded >Listing File Loaded >Symbol table loaded >277488 bytes memory free >% RS >Processor Reset >% GO >Interrupt at address 18 >0019 2818 GOTO ENDLESS_LOOP >% AD INTCON,B,8 >% C >Interrupt at address 18 >0019 2818 GOTO ENDLESS_LOOP >% > > > >Many thanks for any input (good or bad), >Brian. > > "I don't do anything that anybody else in good physical condition and unlimited funds couldn't do" - Bruce Wayne

<x-rich>Hi Brian, >MOVLW B'00000000' ;SET PORTC AS ALL OUTPUTS >TRIS PORTC ; '' >CLRF PORTC ;CLEAR THE PORT The PIC16C74 has two banks of registers. As it happens the TRIS registers are located in the upper bank. I don't think the TRIS PORTC command in your example will work.... I was under the impression something more like this is required... <paraindent><param>left</param> MOVLW B'00000000' ; load W with desired directions BSF STATUS,RP0 ; shift to the upper register bank MOVWF TRISC ; set the C port TRIS BCF STATUS,RP0 ; shift back to the lower registers CLRF PORTC ; clear the C port </paraindent> This is the way the app notes for the 16C74 are written at any rate... If anyone knows this is not required, I would be interested to hear about it... Bob Segrest </x-rich>

Bob's code is correct. Andy At 11:55 AM 2/19/97 -0500, you wrote: >Hi Brian, > >>MOVLW B'00000000' ;SET PORTC AS ALL OUTPUTS >>TRIS PORTC ; '' >>CLRF PORTC ;CLEAR THE PORT > >The PIC16C74 has two banks of registers. As it happens the TRIS registers are located in the upper bank. I don't think the TRIS PORTC command in your example will work.... > >I was under the impression something more like this is required... > >MOVLW B'00000000' ; load W with desired directions >BSF STATUS,RP0 ; shift to the upper register bank >MOVWF TRISC ; set the C port TRIS >BCF STATUS,RP0 ; shift back to the lower registers >CLRF PORTC ; clear the C port > >This is the way the app notes for the 16C74 are written at any rate... If anyone knows this is not required, I would be interested to hear about it... > >Bob Segrest > ================================================================== Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865 Hardware & Software for Industry & R/C Hobbies "Go fast, turn right, and keep the wet side down!" ==================================================================