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;; -*- mode: common-lisp -*-
#|
clasm-6502: An assembler for the 6502 written in Common Lisp.
Copyright (C) 2024 Aleksei Eaves
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|#
;; Rules for converting an addressing mode argument.
(defparameter
*convert-addressing-modes*
'(
(immediate
(lambda (s)
(let ((return-value 0) ; Final return value.
(operand nil)) ; Stores +/- found.
(dotimes (i (length s))
(cond
;; Starting hash
((eq (char s i) #\#)
nil)
;; Hexadecimal value
((eq (char s i) #\$)
(progn (incf i)
(setf return-value
(if (not (equal operand nil))
(funcall operand
return-value
(hex2dec (subseq s i (+ i 2))))
(hex2dec (subseq s i (+ i 2)))))
(incf i)))
;; Plus or Minus
((or (eq (char s i) #\+)
(eq (char s i) #\-))
(setf operand
(read-from-string (subseq s i (+ i 1)))))
;; Interpret character
((and (eq (char s i) #\')
(eq (char s (+ i 2)) #\'))
(progn (incf i)
(setf return-value
(if (not (equal operand nil))
(funcall operand
return-value
(char-code (char s i)))
(char-code (char s i))))
(incf i)))
(t (error "Badly formed immediate instruction."))
))
(mod return-value 256)))
(absolute
(lambda (s)
(list (hex2dec (subseq s 1 3))
(hex2dec (subseq s 3 5)))))
(zero-page
(lambda (s)
(list (hex2dec (subseq s 1 3)))))
(implied
(lambda (s)
nil))
(indirect-absolute
(lambda (s)
(list (hex2dec (subseq s 2 4))
(hex2dec (subseq s 4 6)))))
(absolute-indexed-x
(lambda (s)
(list (hex2dec (subseq s 1 3))
(hex2dec (subseq s 3 5)))))
(absolute-indexed-y
(lambda (s)
(list (hex2dec (subseq s 1 3))
(hex2dec (subseq s 3 5)))))
(zero-page-indexed-x
(lambda (s)
(list (hex2dec (subseq s 1 3)))))
(zero-page-indexed-y
(lambda (s)
(list (hex2dec (subseq s 1 3)))))
(indexed-indirect
(lambda (s)
(list (hex2dec (subseq s 2 4)))))
(indirect-indexed
(lambda (s)
(list (hex2dec (subseq s 2 4)))))
(relative
(lambda (s)
(list (hex2dec (subseq s 1 3))
(hex2dec (subseq s 3 5)))))
(accumulator
(lambda (s)
nil)))))
|
