Queue.zip RS232 circular buffer AT90s2313 J Tidwell
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; 5/99 by Jack Tidwell ;******************************************* ;*Simple & effective rs232 circular buffer * ;* Interupt driven, thus 'transparent' to * ;* User functions * ;******************************************* .include "2313def.inc" .equ BUFSIZE = 10 .def rxhead =r16 .def rxtail =r17 .def tempchar=r18 .DSEG Buf: .byte BUFSIZE .CSEG ;************************ ;* The actual RS232 ISR * ;************************ Rs232ISR: push r1 in r1,SREG ; preserve main OS status reg. push r2 push zl push zh clr r2 ldi zl,low(Buf); ptr to our rxbuffer ldi zh,high(Buf) add zl,rxtail adc zh,r2 in r2,UDR ; get the incomming char st z,r2 ; Buf[rxtail++] = UDR inc rxtail cpi rxtail,BUFSIZE brlo Rs232inx clr rxtail ; Circle around to the first buffer pos. Rs232inx: ;***** Xoff calcs go here ***** pop zh pop zl pop r2 out SREG,r1 ; restore previous status reg pop r1 reti ; return to normal pgm status. ; ;************************** ;* The RS232 FIFO manager * ;************************** Rs232GetByte: clr tempchar cp rxhead,rxtail breq Rs232GetBytexit clr r2 ldi zl,low(Buf); Pointer to the rxbuffer (FIFO) ldi zh,high(Buf) add zl,rxhead adc zh,tempchar ld tempchar,z; tempchar = Buf[rxhead++] inc rxhead cpi rxhead,BUFSIZE brlo Rs232Gbx clr rxhead ; Circle around to the first buffer pos. Rs232Gbx: ;***** Xon calcs go here ***** sec ; This is not need for ASCII data ret ; as a zero value returned in tempchar works Rs232GetBytexit: ; But, for binary data, zero may be valid! clc ; Return 'No' bytes in yet. ret ; ;****************************** ;* And The RS232 GetChar Loop * ;* wait until a char comes in * ;****************************** GetChar: rcall Rs232GetByte brcc GetChar ret ; |