179 lines
4.5 KiB
HTML
179 lines
4.5 KiB
HTML
<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"/><link rel="stylesheet" type="text/css" href="ca65-doc-style.css"/></head><body><a href="ref_index.html"><h1>ip65 technical reference</h1></a><h1>File : ip65/arithmetic.s</h1><h2 id="functions">functions</h2><table><tr><th>function</th><th>description</th></tr><tr><td id="add_16_32">add_16_32</td><td><pre>add a 16bit operand to the 32 bit accumulater
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acc32=acc32+AX
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</pre></td></tr><tr><td id="add_32_32">add_32_32</td><td><pre>add a 32bit operand to the 32 bit accumulater
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acc32=acc32+op32
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</pre></td></tr><tr><td id="cmp_16_16">cmp_16_16</td><td><pre>compare 2 16bit numbers
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on exit, zero flag clear iff acc16==AX
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</pre></td></tr><tr><td id="cmp_32_32">cmp_32_32</td><td><pre>compare 2 32bit numbers
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on exit, zero flag clear iff acc32==op32
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</pre></td></tr><tr><td id="mul_8_16">mul_8_16</td><td><pre>multiply a 16 bit number by an 8 bit number
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acc16=acc16*a
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</pre></td></tr><tr><td id="sub_16_16">sub_16_16</td><td><pre>subtract 2 16 bit numbers
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acc16=acc16-AX
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</pre></td></tr></table><h2 id="variables">variables</h2><table><tr><th>variable</th><th>description</th><th>size (bytes)</th></tr><tr><td id="op32">op32</td><td></td><td></td></tr></table><h2 id="constants">constants</h2><table><tr><th>constants</th><th>description</th><th>value</th></tr><tr><td id="acc16">acc16</td><td>acc16=acc16*a
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</td><td>acc16*a
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</td></tr><tr><td id="acc32">acc32</td><td>acc32=acc32+AX
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</td><td>acc32+AX
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</td></tr></table><h2>implementation</h2><pre id="code">.include "../inc/common.i"
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;helper routines for arithmetic on 32 bit numbers
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;reuse the copy_* zero page locations as pointers for 32bit addition
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.importzp copy_src
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.importzp copy_dest
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acc32 =copy_src ;32bit accumulater (pointer)
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op32 =copy_dest ;32 bit operand (pointer)
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acc16 =acc32 ;16bit accumulater (value, NOT pointer)
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.bss
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temp_ax: .res 2
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.code
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;no 16bit operand as can just use AX
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.exportzp acc32
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.exportzp op32
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.exportzp acc16
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.export add_32_32
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.export add_16_32
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.export sub_16_16
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.export cmp_32_32
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.export cmp_16_16
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.export mul_8_16
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;compare 2 32bit numbers
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;on exit, zero flag clear iff acc32==op32
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cmp_32_32:
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ldy #0
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lda (op32),y
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cmp (acc32),y
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bne @exit
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iny
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lda (op32),y
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cmp (acc32),y
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bne @exit
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iny
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lda (op32),y
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cmp (acc32),y
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bne @exit
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iny
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lda (op32),y
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cmp (acc32),y
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@exit:
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rts
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;compare 2 16bit numbers
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;on exit, zero flag clear iff acc16==AX
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cmp_16_16:
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cmp acc16
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bne @exit
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txa
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cmp acc16+1
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@exit:
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rts
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;subtract 2 16 bit numbers
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;acc16=acc16-AX
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sub_16_16:
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stax temp_ax
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sec
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lda acc16
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sbc temp_ax
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sta acc16
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lda acc16+1
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sbc temp_ax+1
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sta acc16+1
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rts
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;add a 32bit operand to the 32 bit accumulater
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;acc32=acc32+op32
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add_32_32:
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clc
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ldy #0
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lda (op32),y
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adc (acc32),y
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sta (acc32),y
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iny
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lda (op32),y
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adc (acc32),y
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sta (acc32),y
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iny
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lda (op32),y
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adc (acc32),y
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sta (acc32),y
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iny
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lda (op32),y
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adc (acc32),y
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sta (acc32),y
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rts
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;add a 16bit operand to the 32 bit accumulater
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;acc32=acc32+AX
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add_16_32:
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clc
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ldy #0
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adc (acc32),y
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sta (acc32),y
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iny
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txa
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adc (acc32),y
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sta (acc32),y
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iny
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lda #0
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adc (acc32),y
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sta (acc32),y
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iny
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lda #0
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adc (acc32),y
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sta (acc32),y
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rts
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;multiply a 16 bit number by an 8 bit number
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;acc16=acc16*a
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mul_8_16:
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tax
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beq @operand_is_zero
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lda acc16
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sta temp_ax
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lda acc16+1
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sta temp_ax+1
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@addition_loop:
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dex
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beq @done
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clc
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lda acc16
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adc temp_ax
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sta acc16
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lda acc16+1
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adc temp_ax+1
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sta acc16+1
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jmp @addition_loop
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@done:
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rts
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@operand_is_zero:
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sta acc16
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sta acc16+1
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rts
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;-- LICENSE FOR arithmetic.s --
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; The contents of this file are subject to the Mozilla Public License
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; Version 1.1 (the "License"); you may not use this file except in
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; compliance with the License. You may obtain a copy of the License at
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; http://www.mozilla.org/MPL/
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;
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; Software distributed under the License is distributed on an "AS IS"
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; basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the
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; License for the specific language governing rights and limitations
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; under the License.
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;
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; The Original Code is ip65.
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;
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; The Initial Developer of the Original Code is Jonno Downes,
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; jonno@jamtronix.com.
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; Portions created by the Initial Developer are Copyright (C) 2009
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; Jonno Downes. All Rights Reserved.
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; -- LICENSE END --
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</pre></body></html> |