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opcodes.lisp
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opcodes.lisp
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(in-package :6502)
(defasm adc (:docs "Add to Accumulator with Carry")
((#x61 6 2 indirect-x)
(#x65 3 2 zero-page)
(#x69 2 2 immediate)
(#x6d 4 3 absolute)
(#x71 5 2 indirect-y)
(#x75 4 2 zero-page-x)
(#x79 4 3 absolute-y)
(#x7d 4 3 absolute-x))
(let ((result (+ (cpu-ar cpu) (getter) (status-bit :carry))))
(set-flags-if :carry (> result #xff)
:overflow (overflow-p result (cpu-ar cpu) (getter))
:negative (logbitp 7 result)
:zero (zerop (wrap-byte result)))
(setf (cpu-ar cpu) (wrap-byte result))))
(defasm and (:docs "And with Accumulator")
((#x21 6 2 indirect-x)
(#x25 3 2 zero-page)
(#x29 2 2 immediate)
(#x2d 4 3 absolute)
(#x31 5 2 indirect-y)
(#x35 4 2 zero-page-x)
(#x39 4 3 absolute-y)
(#x3d 4 3 absolute-x))
(let ((result (setf (cpu-ar cpu) (logand (cpu-ar cpu) (getter)))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm asl (:docs "Arithmetic Shift Left")
((#x06 5 2 zero-page)
(#x0a 2 1 accumulator)
(#x0e 6 3 absolute)
(#x16 6 2 zero-page-x)
(#x1e 7 3 absolute-x))
(let* ((operand (getter))
(result (wrap-byte (ash operand 1))))
(set-flags-if :carry (logbitp 7 operand)
:zero (zerop result)
:negative (logbitp 7 result))
(setter result)))
(defasm bcc (:docs "Branch on Carry Clear" :track-pc nil)
((#x90 2 2 relative))
(branch-if (zerop (status-bit :carry))))
(defasm bcs (:docs "Branch on Carry Set" :track-pc nil)
((#xb0 2 2 relative))
(branch-if (plusp (status-bit :carry))))
(defasm beq (:docs "Branch if Equal" :track-pc nil)
((#xf0 2 2 relative))
(branch-if (plusp (status-bit :zero))))
(defasm bit (:docs "Test Bits in Memory with Accumulator")
((#x24 3 2 zero-page)
(#x2c 4 3 absolute))
(let ((operand (getter)))
(set-flags-if :zero (zerop (logand (cpu-ar cpu) operand))
:negative (logbitp 7 operand)
:overflow (logbitp 6 operand))))
(defasm bmi (:docs "Branch on Negative Result" :track-pc nil)
((#x30 2 2 relative))
(branch-if (plusp (status-bit :negative))))
(defasm bne (:docs "Branch if Not Equal" :track-pc nil)
((#xd0 2 2 relative))
(branch-if (zerop (status-bit :zero))))
(defasm bpl (:docs "Branch on Positive Result" :track-pc nil)
((#x10 2 2 relative))
(branch-if (zerop (status-bit :negative))))
(defasm brk (:docs "Force Break")
((#x00 7 1 implied))
(let ((pc (wrap-word (1+ (cpu-pc cpu)))))
(stack-push-word pc cpu)
(set-status-bit :break 1)
(stack-push (cpu-sr cpu) cpu)
(set-status-bit :interrupt 1)
(setf (cpu-pc cpu) (get-word #xfffe))))
(defasm bvc (:docs "Branch on Overflow Clear" :track-pc nil)
((#x50 2 2 relative))
(branch-if (zerop (status-bit :overflow))))
(defasm bvs (:docs "Branch on Overflow Set" :track-pc nil)
((#x70 2 2 relative))
(branch-if (plusp (status-bit :overflow))))
(defasm clc (:docs "Clear Carry Flag")
((#x18 2 1 implied))
(set-status-bit :carry 0))
(defasm cld (:docs "Clear Decimal Flag")
((#xd8 2 1 implied))
(set-status-bit :decimal 0))
(defasm cli (:docs "Clear Interrupt Flag")
((#x58 2 1 implied))
(set-status-bit :interrupt 0))
(defasm clv (:docs "Clear Overflow Flag")
((#xb8 2 1 implied))
(set-status-bit :overflow 0))
(defasm cmp (:docs "Compare Memory with Accumulator")
((#xc1 6 2 indirect-x)
(#xc5 3 2 zero-page)
(#xc9 2 2 immediate)
(#xcd 4 3 absolute)
(#xd1 5 2 indirect-y)
(#xd5 4 2 zero-page-x)
(#xd9 4 3 absolute-y)
(#xdd 4 3 absolute-x))
(let ((result (- (cpu-ar cpu) (getter))))
(set-flags-if :carry (not (minusp result))
:zero (zerop result)
:negative (logbitp 7 result))))
(defasm cpx (:docs "Compare Memory with X register")
((#xe0 2 2 immediate)
(#xe4 3 2 zero-page)
(#xec 4 3 absolute))
(let ((result (- (cpu-xr cpu) (getter))))
(set-flags-if :carry (not (minusp result))
:zero (zerop result)
:negative (logbitp 7 result))))
(defasm cpy (:docs "Compare Memory with Y register")
((#xc0 2 2 immediate)
(#xc4 3 2 zero-page)
(#xcc 4 3 absolute))
(let ((result (- (cpu-yr cpu) (getter))))
(set-flags-if :carry (not (minusp result))
:zero (zerop result)
:negative (logbitp 7 result))))
(defasm dec (:docs "Decrement Memory")
((#xc6 5 2 zero-page)
(#xce 6 3 absolute)
(#xd6 6 2 zero-page-x)
(#xde 7 3 absolute-x))
(let ((result (wrap-byte (1- (getter)))))
(setter result)
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm dex (:docs "Decrement X register")
((#xca 2 1 implied))
(let ((result (setf (cpu-xr cpu) (wrap-byte (1- (cpu-xr cpu))))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm dey (:docs "Decrement Y register")
((#x88 2 1 implied))
(let ((result (setf (cpu-yr cpu) (wrap-byte (1- (cpu-yr cpu))))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm eor (:docs "Exclusive OR with Accumulator")
((#x41 6 2 indirect-x)
(#x45 3 2 zero-page)
(#x49 2 2 immediate)
(#x4d 4 3 absolute)
(#x51 5 2 indirect-y)
(#x55 4 2 zero-page-x)
(#x59 4 3 absolute-y)
(#x5d 4 3 absolute-x))
(let ((result (setf (cpu-ar cpu) (logxor (getter) (cpu-ar cpu)))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm inc (:docs "Increment Memory")
((#xe6 5 2 zero-page)
(#xee 6 3 absolute)
(#xf6 6 2 zero-page-x)
(#xfe 7 3 absolute-x))
(let ((result (wrap-byte (1+ (getter)))))
(setter result)
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm inx (:docs "Increment X register")
((#xe8 2 1 implied))
(let ((result (setf (cpu-xr cpu) (wrap-byte (1+ (cpu-xr cpu))))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm iny (:docs "Increment Y register")
((#xc8 2 1 implied))
(let ((result (setf (cpu-yr cpu) (wrap-byte (1+ (cpu-yr cpu))))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm jmp (:docs "Jump Unconditionally" :raw-p t :track-pc nil)
((#x4c 3 3 absolute)
(#x6c 5 3 indirect))
(setf (cpu-pc cpu) (getter)))
(defasm jsr (:docs "Jump to Subroutine" :raw-p t :track-pc nil)
((#x20 6 3 absolute))
(stack-push-word (wrap-word (1+ (cpu-pc cpu))) cpu)
(setf (cpu-pc cpu) (getter)))
(defasm lda (:docs "Load Accumulator from Memory")
((#xa1 6 2 indirect-x)
(#xa5 3 2 zero-page)
(#xa9 2 2 immediate)
(#xad 4 3 absolute)
(#xb1 5 2 indirect-y)
(#xb5 4 2 zero-page-x)
(#xb9 4 3 absolute-y)
(#xbd 4 3 absolute-x))
(let ((result (setf (cpu-ar cpu) (getter))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm ldx (:docs "Load X register from Memory")
((#xa2 2 2 immediate)
(#xa6 3 2 zero-page)
(#xae 4 3 absolute)
(#xb6 4 2 zero-page-y)
(#xbe 4 3 absolute-y))
(let ((result (setf (cpu-xr cpu) (getter))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm ldy (:docs "Load Y register from Memory")
((#xa0 2 2 immediate)
(#xa4 3 2 zero-page)
(#xac 4 3 absolute)
(#xbc 4 3 absolute-x)
(#xb4 4 2 zero-page-x))
(let ((result (setf (cpu-yr cpu) (getter))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm lsr (:docs "Logical Shift Right")
((#x46 5 2 zero-page)
(#x4a 2 1 accumulator)
(#x4e 6 3 absolute)
(#x56 6 2 zero-page-x)
(#x5e 7 3 absolute-x))
(let* ((operand (getter))
(result (ash operand -1)))
(set-flags-if :carry (logbitp 0 operand)
:zero (zerop result)
:negative (logbitp 7 result))
(setter result)))
(defasm nop (:docs "No Operation")
((#xea 2 1 implied))
nil)
(defasm ora (:docs "Bitwise OR with Accumulator")
((#x01 6 2 indirect-x)
(#x05 3 2 zero-page)
(#x09 2 2 immediate)
(#x0d 4 3 absolute)
(#x11 5 2 indirect-y)
(#x15 4 2 zero-page-x)
(#x19 4 3 absolute-y)
(#x1d 4 3 absolute-x))
(let ((result (setf (cpu-ar cpu) (logior (cpu-ar cpu) (getter)))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm pha (:docs "Push Accumulator")
((#x48 3 1 implied))
(stack-push (cpu-ar cpu) cpu))
(defasm php (:docs "Push Processor Status")
((#x08 3 1 implied))
(stack-push (logior (cpu-sr cpu) #x10) cpu))
(defasm pla (:docs "Pull Accumulator from Stack")
((#x68 4 1 implied))
(let ((result (setf (cpu-ar cpu) (stack-pop cpu))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm plp (:docs "Pull Processor Status from Stack")
((#x28 4 1 implied))
(let ((result (logior (stack-pop cpu) #x20)))
(setf (cpu-sr cpu) (logandc2 result #x10))))
(defasm rol (:docs "Rotate Left")
((#x2a 2 1 accumulator)
(#x26 5 2 zero-page)
(#x2e 6 3 absolute)
(#x36 6 2 zero-page-x)
(#x3e 7 3 absolute-x))
(let* ((operand (getter))
(result (wrap-byte (rotate-byte operand 1 cpu))))
(setter result)
(set-flags-if :carry (logbitp 7 operand)
:zero (zerop result)
:negative (logbitp 7 result))))
(defasm ror (:docs "Rotate Right")
((#x66 5 2 zero-page)
(#x6a 2 1 accumulator)
(#x6e 6 3 absolute)
(#x76 6 2 zero-page-x)
(#x7e 7 3 absolute-x))
(let* ((operand (getter))
(result (wrap-byte (rotate-byte operand -1 cpu))))
(setter result)
(set-flags-if :carry (logbitp 0 operand)
:zero (zerop result)
:negative (logbitp 7 result))))
(defasm rti (:docs "Return from Interrupt")
((#x40 6 1 implied))
(setf (cpu-sr cpu) (logior (stack-pop cpu) #x20))
(setf (cpu-pc cpu) (stack-pop-word cpu)))
(defasm rts (:docs "Return from Subroutine" :track-pc nil)
((#x60 6 1 implied))
(setf (cpu-pc cpu) (1+ (stack-pop-word cpu))))
(defasm sbc (:docs "Subtract from Accumulator with Carry")
((#xe1 6 2 indirect-x)
(#xe5 3 2 zero-page)
(#xe9 2 2 immediate)
(#xed 4 3 absolute)
(#xf1 5 2 indirect-y)
(#xf5 4 2 zero-page-x)
(#xf9 4 3 absolute-y)
(#xfd 4 3 absolute-x))
(flet ((flip-bit (position x) (logxor (expt 2 position) x)))
(let* ((operand (getter))
(carry-bit (flip-bit 0 (status-bit :carry)))
(result (- (cpu-ar cpu) operand carry-bit)))
(set-flags-if :zero (zerop (wrap-byte result))
:overflow (overflow-p result (cpu-ar cpu) (flip-bit 7 operand))
:negative (logbitp 7 result)
:carry (not (minusp result)))
(setf (cpu-ar cpu) (wrap-byte result)))))
(defasm sec (:docs "Set Carry Flag")
((#x38 2 1 implied))
(set-status-bit :carry 1))
(defasm sed (:docs "Set Decimal Flag")
((#xf8 2 1 implied))
(set-status-bit :decimal 1))
(defasm sei (:docs "Set Interrupt Flag")
((#x78 2 1 implied))
(set-status-bit :interrupt 1))
(defasm sta (:docs "Store Accumulator")
((#x81 6 2 indirect-x)
(#x85 3 2 zero-page)
(#x8d 4 3 absolute)
(#x91 6 2 indirect-y)
(#x95 4 2 zero-page-x)
(#x99 5 3 absolute-y)
(#x9d 5 3 absolute-x))
(setter (cpu-ar cpu)))
(defasm stx (:docs "Store X register")
((#x86 3 2 zero-page)
(#x8e 4 3 absolute)
(#x96 4 2 zero-page-y))
(setter (cpu-xr cpu)))
(defasm sty (:docs "Store Y register")
((#x84 3 2 zero-page)
(#x8c 4 3 absolute)
(#x94 4 2 zero-page-x))
(setter (cpu-yr cpu)))
(defasm tax (:docs "Transfer Accumulator to X register")
((#xaa 2 1 implied))
(let ((result (setf (cpu-xr cpu) (cpu-ar cpu))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm tay (:docs "Transfer Accumulator to Y register")
((#xa8 2 1 implied))
(let ((result (setf (cpu-yr cpu) (cpu-ar cpu))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm tsx (:docs "Transfer Stack Pointer to X register")
((#xba 2 1 implied))
(let ((result (setf (cpu-xr cpu) (cpu-sp cpu))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm txa (:docs "Transfer X register to Accumulator")
((#x8a 2 1 implied))
(let ((result (setf (cpu-ar cpu) (cpu-xr cpu))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))
(defasm txs (:docs "Transfer X register to Stack Pointer")
((#x9a 2 1 implied))
(setf (cpu-sp cpu) (cpu-xr cpu)))
(defasm tya (:docs "Transfer Y register to Accumulator")
((#x98 2 1 implied))
(let ((result (setf (cpu-ar cpu) (cpu-yr cpu))))
(set-flags-if :zero (zerop result) :negative (logbitp 7 result))))