; Chapter 8 6805 assembly language programs; Jonathan W. Valvano; This software accompanies the book,; Real Time Embedded Systems published by Brooks Cole;; Program 8.24. A double circular linked list used to control the stepper motor.;MC68HC705 or MC68HC708 ;Linked list stored in EEPROMLL:  S10:  dc.b 10    ;Output pattern      dc.b S9-LL ;Next if CW       dc.b S6-LL ;Next if CCWS9:   dc.b 9          dc.b S10-LL       dc.b S5-LL S5:   dc.b 5          dc.b S9-LL       dc.b S6-LL  S6:   dc.b 6         dc.b S5-LL        dc.b S10-LL      ;Global variables stored in RAMPOS:  ds   1   ;0<=POS<=199PT:   ds   1   ;to current state; Program 8.25. Helper functions used to control the stepper motor.; MC68HC705 or MC68HC708 goal: ds  1    ;desired position;Reg A=desired 0<=RegA<=199SEEK: sta goal   ;Save desired       sub POS    ;Go CW or CCW?      beq DONE   ;Skip if equal      bhi HIGH   ;Desired>POS?;Desired<POS      nega       ;(POS-Desired)      cmp #100      blo GOCCW  ;Go CCW if;Desired<POS and POS-Desired<100GOCW: bsr CW     ;Reg A current      cmp goal      bne GOCW   ;POS=Desired?      bra DONEHIGH: cmp #100   ;(Desired-POS)      blo GOCW   ;Go CW if;Desired>POS and Desired-POS<100GOCCW: bsr CCW   ;Reg A current       cmp goal	      bne GOCCW ;POS=Desired?DONE: rts        ;Return