Signetics 2650 & 2636 programming/Tutorial code - State machine

Tutorial code - State machine

This is the code for the tutorial Indexed branching - creating a state machine

; Tutorial State machine
;=============================================================================
SquareState     equ    $1F0E    ;variable indicates state of the Square operation
TriangleState   equ    $1F0F    ;variable indicates state of the Triangle operation
        org     0
reset_vector:                   ; the microprocessor starts here when the reset button is pressed
        bcta,un reset
        org     3
interrupt_vector:               ; interrupts shouldn't happen, but we set this just in case
        retc,un
reset:  
        lodi,r0 $20	        ; initialise program status word
        lpsu                    ; inhibit interrupts, stack pointer=0
        lodi,r0 $02
        lpsl                    ; register bank 0, without carry, logical compare

        eorz    r0
        stra,r0 effects         ;initialise the 74LS378
        stra,r0 objectsize      ;all objects size 0
        bsta,un DefineObjects   ;define all objects 
   
        lodi,r0 $AA
        stra,r0 score12
        stra,r0 score34

        eorz    r0
        stra,r0 effects         ; !invert = 0 

        lodi,r0 0               ;  X / 000              /   0     / 000
        stra,r0 backgnd         ;    / black background / disabled / yellow screen

        lodi,r0 %00011101       ; XX  /  011        /   101
        stra,r0 colours12       ;     / obj1 red / obj2 green

        lodi,r0 40              ;set initial position of two objects
        stra,r0 hc1
        stra,r0 hc2
        stra,r0 vc1
        stra,r0 vc2

        lodi,r0 0
        stra,r0 SquareState
        lodi,r0 0
        stra,r0 TriangleState

endless:
        bsta,un Vsync0          ; make sure VRST hasn't started
        bsta,un Vsync1          ; wait for VRST to start
        loda,r3 SquareState     ; go and make one movement in the Square state-machine
        bsxa    squareLUT,r3 
        loda,r3 TriangleState   ; go and make one movement in the Triangle state-machine
        bsxa    triangleLUT,r3
        bctr,un endless         ; repeat endlessly

;===========================================================================================
; Define the Square state-machine
squareLUT:                       ; look up table connecting index to subroutine
        bcta,un squaretop            ; 0
        bcta,un squareright          ; 3
        bcta,un squarebottom         ; 6
        bcta,un squareleft           ; 9

squaretop:
        loda,r0 hc1		        ; move object 1 right
        addi,r0 1
        stra,r0 hc1
        comi,r0 150
        retc,lt                 ; if reached endpoint
        lodi,r0 3
        stra,r0 SquareState     ;   change state to move down
        retc,un

squareright:
        loda,r0 vc1		        ; move object 1 down
        addi,r0 1
        stra,r0 vc1
        comi,r0 120
        retc,lt                 ; if reached endpoint
        lodi,r0 6
        stra,r0 SquareState     ;   change state to move left
        retc,un

squarebottom:
        loda,r0 hc1		        ; move object 1 left
        subi,r0 1
        stra,r0 hc1
        comi,r0 40
        retc,gt                 ; if reached endpoint
        lodi,r0 9
        stra,r0 SquareState     ;   change state to move up
        retc,un

squareleft:
        loda,r0 vc1		        ; move object 1 up
        subi,r0 1
        stra,r0 vc1
        comi,r0 40
        retc,gt                 ; if reached endpoint
        lodi,r0 0
        stra,r0 SquareState     ;   change state to move right
        retc,un

;===========================================================================================
; Define the Triangle state-machine
triangleLUT:
        bcta,un triangleleft         ; 0
        bcta,un trianglebottom       ; 3
        bcta,un trianglehypo         ; 6

triangleleft:
        loda,r0 vc2		; move object 2 down
        addi,r0 1
        stra,r0 vc2
        comi,r0 140
        retc,lt                 ; if reached endpoint
        lodi,r0 3
        stra,r0 TriangleState   ;   change state
        retc,un

trianglebottom:
        loda,r0 hc2		; move object 2 right
        addi,r0 1
        stra,r0 hc2
        comi,r0 140
        retc,lt                 ; if reached endpoint
        lodi,r0 6
        stra,r0 TriangleState   ;   change state
        retc,un

trianglehypo:
        loda,r0 hc2		; move object 2 left
        subi,r0 1
        stra,r0 hc2
        loda,r0 vc2		; move object 2 up
        subi,r0 1
        stra,r0 vc2
        comi,r0 40
        retc,gt                 ; if reached endpoint
        lodi,r0 0
        stra,r0 TriangleState   ;   change state
        retc,un



;===================================================================
; subroutine  -  define shapes and position of all objects
                       
DefineObjects:
        lodi,r3 $0E
        lodi,r0 $FF
loopDS:                         
        stra,r0 shape1,r3-      ; create rectangular shapes
        stra,r0 shape2,r3
        stra,r0 shape3,r3
        stra,r0 shape4,r3
        brnr,r3 loopDS

        retc,un

;=================================================================
; subroutine - wait for VRST to clear
Vsync0:                       
        tpsu    sense
        bctr,eq Vsync0          ; wait for Sense bit to clear
        retc,un
;=================================================================
; subroutine - wait for VRST to set
Vsync1:         
        tpsu    sense           ; wait for Sense bit to be set
        bctr,lt Vsync1
        retc,un