📄 chap3.asm
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; Chapter 3 6811 assembly language programs; Jonathan W. Valvano; This software accompanies the book,; Real Time Embedded Systems published by Brooks Cole;; Program 3.3. Assembly language routines to initialize and output to a printer.; MC68HC11A8; PortB is DATA, STRB=GOInit clr PIOC rtsOut staa PORTB ldd #2857OLoop subd #1 ;[4] bne OLoop ;[3] rts; Program 3.6. 6811 or 6812 assembly language routine to create an accurate time delay.; 6811 or 6812; Reg D is the number of cycles to wait; can range from 25 to 32767Wait addd TCNT time at the end of delayLoop cpd TCNT wait for Endt-TCNT>0 bpl Loop rts; Program 3.8. Assembly language routines to initialize and read from an A/D.; MC68HC11A8; PortC is DATA, STRB=GOInit ldaa #$01 ;INVB=1 staa PIOC clr DDRC rtsIn staa PORTB ;GO pulse mul ;[10] ldaa PORTC rts; Program 3.10. Assembly language routines to initialize and read from a keyboard.; MC68HC11A8; PortC=DATA, STRA=STROBEInit ldaa #$02 ;EGA=1 staa PIOC ldaa #$80 ;PC7=output staa DDRC ldaa PIOC ;STAF=0 ldaa PORTCL clr PORTC ;PC7=0 rtsIn ldaa PIOC ; wait for STAF bpl In ldaa PORTCL rts; Program 3.12. Assembly language routines to initialize and read from an A/D.; MC68HC11A8; PortC=DATA STRA=DONE STRB=GOInit ldaa #$03 ;EGA=1, INVB=1 staa PIOC ldaa #$00 ;PC=input staa DDRC ldaa PIOC ;STAF=0 ldaa PORTCL rtsIn staa PORTB ;GO pulseloop ldaa PIOC ;wait for STAF bita #$80 beq loop ldaa PORTCL rts; Program 3.14. Handshaking assembly language routines to initialize and read from a sensor.; MC68HC11A8; PortC=DATA STRA=READY STRB=ACKInit ldaa #$13 ;Input hndshake staa PIOC ldaa #$00 ;PC=input staa DDRC ldaa PIOC ;STAF=0 ldaa PORTCL rtsIn ldaa PIOC ;wait for STAF bita #$80 beq loop ldaa PORTCL ;read DATA rts; Program 3.15. Example comment detailing what and why a value is used to initialize a control register.; PortC ritual, Set PC7-PC0 inputs = sensor DATA; PIOC ($1002); 7 STAF Read Only Set on rise of STRA; 6 STAI 0 Gadfly, no interrupts; 5 CWOM 0 Normal outputs; 4 HNDS 1 Input handshake; 3 OIN 0; 2 PLS 0 ACK=STRB goes to 0 on rise of READY; 1 EGA 1 STAF set on rise of READY=STRA; 0 INVB 1 ACK=STRB goes to 1 on a ReadCL ; STRB=ACK signifies 6811 status 0 means busy,1 means done; STRA=READY rising edge when new sensor data is ready; Program 3.17. Handshaking assembly language routines to initialize and write to a printer.; MC68HC11A8; PC=DATA STRA=READY STRB=START; 7 STAF Set on rise of STRA; 6 STAI 0 Gadfly, no interrpt; 5 CWOM 0 Normal outputs; 4 HNDS 1 Output handshake; 3 OIN 1; 2 PLS 1 Pulse on Write CL; 1 EGA 1 STAF set on ( READY; 0 INVB 0 Negative logic pulse Init ldaa #$1E ;Output hndshke staa PIOC ldaa #$FF ;PC=output staa DDRC rtsOut staa PORTCL ;out, pulsewait ldab PIOC ;wait for STAF bitb #$80 beq wait rts; Program 3.19. Assembly language initialization of the DS1620; MC68HC11A8; PD5=RST PD4=CLK PD3=DQInit ldaa #$38 ;PD5-3 output staa DDRD ldaa #$18 ;RST=0,CLK=1 staa PORTD ;DQ=1 rts; Program 3.21. Assembly language helper functions for the DS1620; MC68HC11A8;output 8 bits, Reg A=dataout8 ldab #8 ;8 bitsclop bclr 0,x,#$10 ;CLK=0 lsra ;lsb first bcc set0 bset 0,x,#$08 ;DQ=1 bra nextset0 bclr 0,x,#$08 ;DQ=0next bset 0,x,#$10 ;CLK=1 decb bne clop rtsstart ldx #PORTD bset 0,x,#$20 ;RST=1 ldaa #$EE bsr out8 bclr 0,x,#$20 ;RST=0 rtsstop ldx #PORTD bset 0,x,#$20 ;RST=1 ldaa #$22 bsr out8 bclr 0,x,#$20 ;RST=0 rts; Program 3.23. Assembly language functions to set the configuration register on the DS1620; MC68HC11A8config ldx #PORTD psha bset 0,x,#$20 ;RST=1 ldaa #$0C bsr out8 pula bsr out8 bclr 0,x,#$20 ;RST=0 rts; Program 3.25. Assembly language 9-bit output helper function for the DS1620; MC68HC11A8;output 9 bits, Reg D=dataout9 ldx #9 ;9 bitsolop bclr 0,x,#$10 ;CLK=0 lsrd ;lsb first bcc oset0 bset 0,x,#$08 ;DQ=1 bra onextoset0 bclr 0,x,#$08 ;DQ=0onext bset 0,x,#$10 ;CLK=1 dex bne olop rts; Program 3.26. Assembly language functions to set the threshold registers on the DS1620; MC68HC11A8;Reg D is temperature valueWriteTH psha pshb ldx #PORTD bset 0,x,#$20 ;RST=1 ldaa #$01 bsr out8 pulb pula bsr out9 bclr 0,x,#$20 ;RST=0 rts;Reg D is temperature valueWriteTL psha pshb ldx #PORTD bset 0,x,#$20 ;RST=1 ldaa #$02 bsr out8 pulb pula bsr out9 bclr 0,x,#$20 ;RST=0 rts; Program 3.28. Assembly language functions to read the configuration register on the DS1620; MC68HC11A8;input 8 bits, Reg A=datain8 ldy #8 ;8 bits ldaa DDRD anda #$F7 ;DQ input staa DDRDilop bclr 0,x,#$10 ;CLK=0 lsra ;lsb first brclr 0,x,#$08,inext oraa #$80 ;DQ=1inext bset 0,x,#$10 ;CLK=1 dey bne ilop ldab DDRD orab #$08 ;DQ output stab DDRD rts;Reg A is config valueReadConfig ldx #PORTD bset 0,x,#$20 ;RST=1 ldaa #$AC bsr out8 bsr in8 bclr 0,x,#$20 ;RST=0 rts; Program 3.29. Assembly language 9-bit read helper function for the DS1620; MC68HC11A8;input 9 bits, Reg D=datain9 ldy #9 ;9 bits ldaa DDRD anda #$F7 ;DQ input staa DDRD clrajlop bclr 0,x,#$10 ;CLK=0 lsrd ;lsb first brclr 0,x,#$08,jnext oraa #$01 ;DQ=1jnext bset 0,x,#$10 ;CLK=1 dey bne jlop psha ldaa DDRD oraa #$08 ;DQ output staa DDRD pula rts; Program 3.30. Assembly language functions to read the temperatures from the DS1620; MC68HC11A8;Reg D returned as TH valueReadTH ldx #PORTD bset 0,x,#$20 ;RST=1 ldaa #$A1 bsr out8 bsr in9 bclr 0,x,#$20 ;RST=0 rts;Reg D returned as TL valueReadTL ldx #PORTD bset 0,x,#$20 ;RST=1 ldaa #$A2 bsr out8 bsr in9 bclr 0,x,#$20 ;RST=0 rts;Reg D returned as TemperatureReadT ldx #PORTD bset 0,x,#$20 ;RST=1 ldaa #$AA bsr out8 bsr in9 bclr 0,x,#$20 ;RST=0 rts⌨️ 快捷键说明
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