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- #lang racket
-
- (struct mem
- (regs pc sp flags bank))
-
- (define (make-mem [start #x00] [bs '()])
- (set-bytes start bs
- (mem (make-regs)
- start
- 0
- 0
- (make-bank))))
-
- (define (make-regs)
- (make-vector 8 0))
-
- (define (get-zero mem)
- (bitwise-bit-set? (mem-flags mem) 7))
-
- (define (get-carry mem)
- (bitwise-bit-set? (mem-flags mem) 4))
-
- (define (get-reg x mem)
- (if (and (< x 8) (>= x 0))
- (let ([regs (mem-regs mem)])
- (if (not (= x 6))
- (vector-ref regs x)
- (let([bank (mem-bank mem)]
- [h (vector-ref regs 4)]
- [l (vector-ref regs 5)])
- (vector-ref bank (make-16b-addr h l)))))
- (error "unknown register index")))
-
- (define (set-reg x val m)
- (if (and (< x 8) (>= x 0))
- (let ([regs (mem-regs m)])
- (if (not (= x 6))
- (let ([newregs (vector-copy regs)])
- (vector-set! newregs x (mod-8bit val))
- (struct-copy mem m [regs newregs]))
- (let ([newbank (vector-copy (mem-bank m))]
- [h (vector-ref regs 4)]
- [l (vector-ref regs 5)])
- (vector-set! newbank (make-16b-addr h l) (mod-8bit val))
- (struct-copy mem m [bank newbank]))))
- (error "unknown register index")))
-
- (define (make-bank [def #x00])
- (make-vector 65536 def))
-
- (define (mod-8bit val)
- (modulo val 256))
-
- (define (mod-16bit val)
- (modulo val 65536))
-
- (define (set-pc addr m)
- (begin
- (struct-copy mem m [pc (mod-16bit addr)])))
-
- (define (set-flags f m)
- (begin
- (struct-copy mem m [flags (mod-8bit f)])))
-
- (define (get-byte addr m)
- (let ([b (mem-bank m)])
- (if (and (>= addr 0)
- (< addr (vector-length b)))
- (vector-ref b addr)
- (error (format "address ~a out of bounds" addr)))))
-
- (define (set-byte addr val m)
- (let ([b (mem-bank m)])
- (if (and (>= addr 0)
- (< addr (vector-length b)))
- (let ([newbank (vector-copy b)])
- (vector-set! newbank addr (mod-8bit val))
- (struct-copy mem m [bank newbank]))
- (error (format "address ~a out of bounds" addr)))))
-
- (define (set-bytes addr bs m)
- (if (null? bs)
- m
- (set-bytes (mod-16bit (add1 addr))
- (cdr bs)
- (set-byte addr (car bs) m))))
-
- (define (get-x byte)
- (arithmetic-shift (bitwise-and #b11000000 byte) -6))
-
- (define (get-y byte)
- (arithmetic-shift (bitwise-and #b00111000 byte) -3))
-
- (define (get-z byte)
- (bitwise-and #b00000111 byte))
-
- (define (inc-sp m)
- (struct-copy mem m [sp (add1 (mem-sp m))]))
-
- (define (inc-pc m)
- (struct-copy mem m [pc (add1 (mem-pc m))]))
-
- (define (make-16b-addr x y)
- (bitwise-ior y (arithmetic-shift x 8)))
-
- (define (make-8b-ld-reg-imm y m)
- (letrec ([pc (mem-pc m)]
- [x (get-byte pc m)])
- (cons (8b-ld-reg-imm y x)
- (set-pc (add1pc pc) m))))
-
- (define (make-jp cc m)
- (letrec ([pc (mem-pc m)]
- [y (get-byte pc m)]
- [npc (add1pc pc)]
- [x (get-byte npc m)]
- [addr (make-16b-addr x y)]
- [cs (cc-tab cc)])
- (cons (jp cs addr) (set-pc (add1pc npc) m))))
-
- (define (cc-tab cc)
- (case cc
- [(0) 'NZ]
- [(1) 'Z]
- [(2) 'NC]
- [(3) 'C]
- [else 'uncond]))
-
- (define (make-8b-ld-reg-reg y z m)
- (cons (8b-ld-reg-reg y z)
- m))
-
- (define (make-alu-imm z m)
- (letrec ([pc (mem-pc m)]
- [x (get-byte pc m)])
- (cons (case z
- [(0) (8b-add-imm x)]
- [(1) (8b-adc-imm x)]
- [(2) (8b-sub-imm x)]
- [(3) (8b-sbc-imm x)]
- [(4) (8b-and-imm x)]
- [(5) (8b-xor-imm x)]
- [(6) (8b-or-imm x)]
- [(7) (8b-cp-imm x)]
- [else (nop)])
- (inc-pc m))))
-
- (define (make-8b-inc-dec-reg y z m)
- (cons ((case z
- [(4) 8b-inc-reg]
- [(5) 8b-dec-reg]) y)
- m))
-
- (define (make-alu-reg y z m)
- (cons (case y
- [(0) (8b-add-reg z)]
- [(1) (8b-adc-reg z)]
- [(2) (8b-sub-reg z)]
- [(3) (8b-sbc-reg z)]
- [(4) (8b-and-reg z)]
- [(5) (8b-xor-reg z)]
- [(6) (8b-or-reg z)]
- [(7) (8b-cp-reg z)])
- m))
-
- (define (make-nop m)
- (cons (nop) m))
-
- (define (make-stop m)
- (cons 'STOP m))
-
- (define (jp cc addr)
- (case cc
- [(uncond) (jp-uncond addr)]
- [else (jp-cond cc addr)]))
-
- (define (8b-ld-reg-imm reg imm)
- (lambda (m)
- (set-reg reg imm m)))
-
- (define (8b-ld-reg-reg dst src)
- (lambda (m)
- (set-reg dst
- (get-reg src m)
- m)))
-
- (define (8b-inc-reg r)
- (lambda (m)
- (let ([a (mod-8bit (add1 (get-reg r m)))])
- (set-flags
- (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00))
- (set-reg r a m)))))
-
- (define (8b-dec-reg r)
- (lambda (m)
- (let ([a (mod-8bit (sub1 (get-reg r m)))])
- (set-flags
- (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- #b01000000)
- (set-reg r a m)))))
-
- (define (jp-cond cc addr)
- (lambda (m)
- (let ([c (get-carry m)]
- [z (get-zero m)])
- (if (case cc
- [(NZ) (not z)]
- [(Z) z]
- [(NC) (not c)]
- [(C) c])
- (set-pc addr m)
- m))))
-
- (define (jp-uncond addr)
- (lambda (m)
- (set-pc addr m)))
-
- (define (8b-add-imm v)
- (lambda (m)
- (let ([a (+ (get-reg 7 m)
- (mod-8bit v))])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- (set-reg 7 (mod-8bit a) m)))))
-
- (define (8b-sbc-imm v)
- (lambda (m)
- (letrec ([c (bitwise-and #b00010000 (mem-flags m))]
- [a (- (get-reg 7 m)
- (mod-8bit v)
- c)])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- (set-reg 7 (mod-8bit a) m)))))
-
- (define (8b-sub-imm v)
- (lambda (m)
- (let ([a (- (get-reg 7 m)
- (mod-8bit v))])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- (set-reg 7 (mod-8bit a) m)))))
-
- (define (8b-cp-imm v)
- (lambda (m)
- (let ([a (- (get-reg 7 m)
- (mod-8bit v))])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- m))))
-
- (define (8b-adc-imm v)
- (lambda (m)
- (letrec ([c (bitwise-and #b00010000 (mem-flags m))]
- [a (+ (get-reg 7 m)
- (mod-8bit v)
- c)])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- (set-reg 7 (mod-8bit a) m)))))
-
- (define (8b-add-reg r)
- (lambda (m)
- (let ([a (+ (get-reg 7 m)
- (get-reg r m))])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- (set-reg 7 (mod-8bit a) m)))))
-
- (define (8b-sbc-reg r)
- (lambda (m)
- (letrec ([c (bitwise-and #b00010000 (mem-flags m))]
- [a (- (get-reg 7 m)
- (get-reg r m)
- c)])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- (set-reg 7 (mod-8bit a) m)))))
-
- (define (8b-sub-reg r)
- (lambda (m)
- (let ([a (- (get-reg 7 m)
- (get-reg r m))])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- (set-reg 7 (mod-8bit a) m)))))
-
- (define (8b-cp-reg r)
- (lambda (m)
- (let ([a (- (get-reg 7 m)
- (get-reg r m))])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- m))))
-
- (define (8b-adc-reg r)
- (lambda (m)
- (letrec ([c (bitwise-and #b00010000 (mem-flags m))]
- [a (+ (get-reg 7 m)
- (get-reg r m)
- c)])
- (set-flags (bitwise-ior (if (= a 0) #b10000000 #x00)
- (if (>= a 16) #b00100000 #x00)
- (if (>= a 256) #b00010000 #x00))
- (set-reg 7 (mod-8bit a) m)))))
-
- (define (8b-xor-reg r)
- (lambda (m)
- (let ([a (bitwise-xor (get-reg 7 m)
- (get-reg r m))])
- (set-flags (if (= a 0) #b10000000 #x00)
- (set-reg 7 a m)))))
-
- (define (8b-and-reg r)
- (lambda (m)
- (let ([a (bitwise-and (get-reg 7 m)
- (get-reg r m))])
- (set-flags (if (= a 0) #b10000000 #x00)
- (set-reg 7 a m)))))
-
- (define (8b-or-reg r)
- (lambda (m)
- (let ([a (bitwise-ior (get-reg 7 m)
- (get-reg r m))])
- (set-flags (if (= a 0) #b10000000 #x00)
- (set-reg 7 a m)))))
-
- (define (8b-xor-imm imm)
- (lambda (m)
- (let ([a (bitwise-xor (get-reg 7 m)
- (mod-8bit imm))])
- (set-flags (if (= a 0) #b10000000 #x00)
- (set-reg 7 a m)))))
-
- (define (8b-or-imm imm)
- (lambda (m)
- (let ([a (bitwise-ior (get-reg 7 m)
- (mod-8bit imm))])
- (set-flags (if (= a 0) #b10000000 #x00)
- (set-reg 7 a m)))))
-
- (define (8b-and-imm imm)
- (lambda (m)
- (let ([a (bitwise-and (get-reg 7 m)
- (mod-8bit imm))])
- (set-flags (if (= a 0) #b10000000 #x00)
- (set-reg 7 a m)))))
-
- (define (nop)
- (lambda (m) m))
-
- (define (display-byte-hex v)
- (~a #:align 'right #:left-pad-string "0" #:width 2
- (format "~x" v)))
-
- (define (display-word-hex v)
- (~a #:align 'right #:left-pad-string "0" #:width 4
- (format "~x" v)))
-
- (define (display-bin v)
- (~a #:left-pad-string "0" #:width 8 #:align 'right
- (format "~b" v)))
-
- (define (print-regs m)
- (letrec ([regs (mem-regs m)]
- [F (display-byte-hex (mem-flags m))]
- [B (display-byte-hex (vector-ref regs 0))]
- [C (display-byte-hex (vector-ref regs 1))]
- [D (display-byte-hex (vector-ref regs 2))]
- [E (display-byte-hex (vector-ref regs 3))]
- [h (vector-ref regs 4)]
- [l (vector-ref regs 5)]
- [H (display-byte-hex (vector-ref regs 4))]
- [L (display-byte-hex (vector-ref regs 5))]
- [HL-ind (display-byte-hex (get-byte (make-16b-addr h l) m))]
- [A (display-byte-hex (vector-ref regs 7))])
- (displayln (format "BC: $~a~a, DE: $~a~a" B C D E))
- (displayln (format "HL: $~a~a, AF: $~a~a" H L A F))
- (displayln (format "(HL): $~a" HL-ind))
- (void)))
-
- (define (print-state m)
- (displayln (format "PC: $~a, SP: $~a, Flags: %~a"
- (display-word-hex (mem-pc m))
- (display-word-hex (mem-sp m))
- (display-bin (mem-flags m)))))
-
- (define (print-part-bank start count m)
- (define (print-mem v)
- (display (format " $~a" (display-byte-hex v))))
- (let ([s (display-word-hex start)]
- [e (display-word-hex (mod-16bit (+ start (sub1 count))))])
- (display (format "$~a >" s))
- (let ([splice (vector-take
- (vector-drop (mem-bank m) start)
- count)])
- (vector-map print-mem splice))
- (display (format " < $~a\n" e) ))
- (void))
-
- (define (add1pc pc)
- (mod-16bit (add1 pc)))
-
- (define (within x y z)
- (and (>= x y) (<= x z)))
-
- (define (decode-op m)
- (letrec ([pc (mem-pc m)]
- [op (get-byte pc m)]
- [npc (add1pc pc)]
- [x (get-x op)]
- [y (get-y op)]
- [z (get-z op)])
- (cond
- [(= #x00 op) (make-nop (set-pc npc m))]
- [(= #x10 op) (make-stop (set-pc npc m))]
- [(= #xC3 op) (make-jp 'uncond (set-pc npc m))]
- [(and (= 0 x) (within z 4 5))
- (make-8b-inc-dec-reg y z (set-pc npc m))]
- [(= 1 x)
- (make-8b-ld-reg-reg y z (set-pc npc m))]
- [(= 2 x)
- (make-alu-reg y z (set-pc npc m))]
- [(and (= 3 x) (= z 2) (within y 0 3))
- (make-jp y (set-pc npc m))]
- [(and (= 3 x) (= z 6))
- (make-alu-imm y (set-pc npc m))]
- [(and (= 0 x) (= 6 z))
- (make-8b-ld-reg-imm y (set-pc npc m))]
- [else (make-nop (set-pc npc m))])))
-
- (define (test-vm start bank-start bank-count bs)
- (let ([m (make-mem start bs)])
- (define (fin m)
- (begin (print-state m)
- (print-regs m)
- (print-part-bank bank-start bank-count m)))
- (define (run-op m)
- (displayln (format "executing: $~a @ $~a"
- (display-byte-hex (get-byte (mem-pc m) m))
- (display-word-hex (mem-pc m))))
- (letrec ([op-pc (decode-op m)]
- [op (car op-pc)]
- [newmem (cdr op-pc)])
- (if (and (not (procedure? op))
- (eq? op 'STOP))
- (fin newmem)
- (begin
- ;(print-state newmem)
- ;(print-regs newmem)
- (run-op (op newmem))))))
- (run-op m)))
-
- (define (run-vm start bank-start bank-count bs)
- (let ([m (make-mem start bs)])
- (define (fin m)
- (begin (print-state m)
- (print-regs m)
- (print-part-bank bank-start bank-count m)))
- (define (run-op m)
- (letrec ([op-pc (decode-op m)]
- [op (car op-pc)]
- [newmem (cdr op-pc)])
- (if (and (not (procedure? op))
- (eq? op 'STOP))
- (fin newmem)
- (run-op (op newmem)))))
- (run-op m)))
-
- (provide (all-defined-out))
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