mirror of
https://github.com/sehugg/8bitworkshop.git
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475 lines
9.4 KiB
C
475 lines
9.4 KiB
C
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/**
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AstroLibre
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An open source Bally Astrocade BIOS implementation in C
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by Steven Hugg (@sehugg) for 8bitworkshop.com
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To the extent possible under law, the author(s) have
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dedicated all copyright and related and neighboring
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rights to this software to the public domain worldwide.
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This software is distributed without any warranty.
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See: http://creativecommons.org/publicdomain/zero/1.0/
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**/
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//#resource "astrocade.inc"
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//#link "biosasm.s"
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// demo code
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//#link "test1.s"
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// music processor
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//#link "bmusic.c"
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// input
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//#link "input.c"
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// graphics
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//#link "gfx.c"
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#include <string.h>
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#include "bios.h"
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// uncomment to make code better, but slower compile
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#pragma opt_code_speed
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// start @ $4FCE
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volatile word MUZPC; // music PC
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volatile word MUZSP; // music SP
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volatile byte PVOLAB; // channels A and B volume
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volatile byte PVOLMC; // channel C volume and noise mask
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volatile byte VOICES; // voice smask
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volatile byte CT[8]; // counter timers
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// for SENTRY
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volatile byte CNT;
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volatile byte SEMI4S;
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volatile byte OPOT[4];
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volatile byte KEYSEX;
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volatile byte OSW[4];
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volatile word COLLST;
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volatile byte DURAT; // note duration
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volatile byte TMR60; // 1/60 sec timer
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volatile byte TIMOUT; // blackout timer
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volatile byte GTSECS; // seconds timer
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volatile byte GTMINS; // minutes timer
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unsigned long RANSHT; // RNG
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byte NUMPLY; // # players
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byte ENDSCR[3]; // end score
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byte MRLOCK; // magic register lock out
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byte GAMSTB; // game status
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byte PRIOR; // music protect
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byte SENFLG; // sentry control
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byte* UMARGT; // user mask table (-64 bytes)
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word* USERTB; // user routine table (-128 bytes)
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// from bmusic.c
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extern void music_update(void);
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// INTERRUPT HANDLER
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//#define USE_ALT_REGS
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void hw_interrupt()
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#ifdef USE_ALT_REGS
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__naked {
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__asm__("ex af,af'");
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__asm__("exx");
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#else
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__interrupt {
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#endif
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CT[0]++;
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CT[1]++;
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CT[2]++;
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CT[3]++;
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if (++TMR60 == 60) {
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TMR60 = 0;
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++TIMOUT;
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KEYSEX |= 0x80; // notify SENTRY
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if (++GTSECS == 60) {
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GTMINS++;
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}
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}
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// TODO?
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if (VOICES) {
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if (DURAT) {
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DURAT--;
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} else {
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music_update();
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}
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}
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#ifdef USE_ALT_REGS
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__asm__("exx");
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__asm__("ex af,af'");
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__asm__("ei");
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__asm__("reti");
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#endif
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}
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void add_counters(byte mask, byte delta) {
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byte i = 0;
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while (mask) {
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if (mask & 1) {
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if (CT[i]) {
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// notify SENTRY if counters go to 0
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if (!(CT[i] += delta)) {
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SENFLG |= 1<<i;
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}
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}
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}
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mask >>= 1;
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i++;
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}
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}
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void STIMER() {
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}
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void CTIMER() {
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}
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void TIMEZ() {
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// updates game timer, blackout timer, and music processor
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}
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void TIMEY() {
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add_counters(0x0f, -1);
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}
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void TIMEX() {
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}
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void DECCTS(ContextBlock *ctx) {
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add_counters(_C, -1);
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}
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// INTERPRETER
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void INTPC(ContextBlock *ctx) {
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while (ctx->params[0] > 2) { // 0,2 = exit
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SYSCALL(ctx);
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}
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ctx->params++; // skip EXIT opcode
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}
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// never called, hopefully
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void EXIT(ContextBlock *ctx) {
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ctx;
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}
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// jumps to HL
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void RCALL(ContextBlock *ctx) {
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((Routine*)_HL)();
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}
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// start interpreting at HL
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void MCALL(ContextBlock *ctx) {
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ctx->params = (byte*)_HL;
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while (ctx->params[0] != 8) { // 8 = MRET
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SYSCALL(ctx);
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}
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}
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// exit MCALL loop
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void MRET(ContextBlock *ctx) {
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ctx; // TODO
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}
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void NOOP(ContextBlock *ctx) {
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ctx;
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}
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// jump within MCALL
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void MJUMP(ContextBlock *ctx) {
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ctx->params = (byte*) _HL; // TODO?
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}
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void suckParams(ContextBlock *ctx, byte argmask) {
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byte* dest = (byte*) ctx;
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byte* src = ctx->params;
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if (argmask & REG_IX) {
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_IXL = *src++;
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_IXH = *src++;
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}
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if (argmask & REG_E)
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_E = *src++;
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if (argmask & REG_D)
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_D = *src++;
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if (argmask & REG_C)
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_C = *src++;
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if (argmask & REG_B)
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_B = *src++;
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if (argmask & REG_A)
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_A = *src++;
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if (argmask & REG_HL) {
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_L = *src++;
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_H = *src++;
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}
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ctx->params = src;
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}
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void SUCK(ContextBlock* ctx) {
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suckParams(ctx, _B);
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}
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const void* const actint_vec = &hw_interrupt;
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void ACTINT(ContextBlock *ctx) {
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ctx;
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__asm
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LD BC,#(_actint_vec) ; upper 8 bits of address
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LD A,B
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LD I,A
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IM 2 ; mode 2
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EI ; enable interrupts
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__endasm;
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hw_inlin = 200;
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hw_infbk = (byte) &actint_vec;
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hw_inmod = 0x8;
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TIMEZ();
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TIMEY();
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}
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// Outputs D to port 0A, B to port 09, A to port 0E.
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void SETOUT(ContextBlock *ctx) {
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hw_verbl = _D;
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hw_horcb = _B;
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hw_inmod = _A;
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}
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// set entire palette at once (8 bytes to port 0xb)
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// bytes in array should be in reverse
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void set_palette(byte palette[8]) __z88dk_fastcall;
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// sets color palettes from (HL)
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void COLSET(ContextBlock *ctx) {
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set_palette((byte*)_HL);
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}
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// Stores A in BC bytes starting at location DE.
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void FILL(ContextBlock *ctx) {
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byte* dest = (byte*) _DE;
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word count = _BC;
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byte val = _A;
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memset(dest, val, count);
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}
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void wait_vsync() {
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byte x = TMR60;
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while (x == TMR60) ; // wait until timer/60 changes
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}
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void PAWS(ContextBlock *ctx) {
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while (_B--) {
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wait_vsync();
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}
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}
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// MATH
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void MOVE(ContextBlock *ctx) {
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memcpy((byte*)_DE, (const byte*)_HL, _BC);
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}
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word bcdadd8(byte a, byte b, byte c);
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void BCDADD(ContextBlock *ctx) {
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byte* dest = (byte*) _DE;
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const byte* src = (const byte*) _HL;
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byte n = _B;
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byte carry = 0;
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while (n--) {
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byte a = *src++;
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byte b = *dest;
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word r = bcdadd8(a,b,carry);
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carry = (r>>8);
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*dest++ = r;
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}
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}
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void RANGED(ContextBlock *ctx) {
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/* Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs" */
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RANSHT ^= RANSHT << 13;
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RANSHT ^= RANSHT >> 17;
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RANSHT ^= RANSHT << 5;
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if (_A == 0) {
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_A = (byte)RANSHT;
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} else {
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_A = (byte)(RANSHT % _A);
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}
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}
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void INDEXB(ContextBlock *ctx) {
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word addr = _HL + _A;
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_HL = addr;
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_A = *((byte*)addr);
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}
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void INDEXW(ContextBlock *ctx) {
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word addr = _HL + _A*2;
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_HL = addr;
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_DE = *((word*)addr);
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}
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void INDEXN(ContextBlock *ctx) {
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byte ofs = _C;
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word addr = _HL + ofs/2;
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byte val = *((byte*)addr);
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_A = (ofs & 1) ? (val>>4) : (val&0xf);
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}
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// input
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extern const byte KCTASC_TABLE[25];
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void KCTASC(ContextBlock *ctx) {
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_A = KCTASC_TABLE[_B];
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}
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// music
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void BMUSIC(ContextBlock *ctx) {
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VOICES = _A;
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MUZPC = _HL;
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MUZSP = _IX;
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DURAT = 0;
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}
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void EMUSIC(ContextBlock *ctx) {
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ctx;
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VOICES = 0;
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}
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// externals
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extern void SENTRY(ContextBlock *ctx);
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extern void DOIT(ContextBlock *ctx);
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extern void DOITB(ContextBlock *ctx);
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extern void RECTAN(const ContextBlock *ctx);
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extern void WRITR(const ContextBlock *ctx);
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extern void WRITP(const ContextBlock *ctx);
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extern void WRIT(const ContextBlock *ctx);
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extern void CHRDIS(const ContextBlock *ctx);
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extern void STRDIS(const ContextBlock *ctx);
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extern void DISNUM(const ContextBlock *ctx);
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// table
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const SysCallEntry SYSCALL_TABLE[64] = {
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/* 0 */
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{ &INTPC, 0 },
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{ &EXIT, 0 },
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{ &RCALL, REG_HL },
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{ &MCALL, REG_HL },
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{ &MRET, 0 },
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/* 10 */
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{ &MJUMP, REG_HL },
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{ &SUCK, REG_B },
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{ &ACTINT, 0 },
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{ &DECCTS, REG_C },
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{ &BMUSIC, REG_HL|REG_IX|REG_A },
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/* 20 */
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{ &EMUSIC, },
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{ &SETOUT, REG_D|REG_B|REG_A },
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{ &COLSET, REG_HL },
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{ &FILL, REG_A|REG_BC|REG_DE },
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{ &RECTAN, REG_A|REG_B|REG_C|REG_D|REG_E },
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/* 30 */
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{ &NOOP, REG_HL|REG_IX }, // VWRITR
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{ &WRITR, REG_E|REG_D|REG_A|REG_HL },
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{ &WRITP, REG_E|REG_D|REG_A|REG_HL },
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{ &WRIT, REG_E|REG_D|REG_C|REG_B|REG_A|REG_HL },
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{ &NOOP, REG_E|REG_D|REG_C|REG_B|REG_A|REG_HL }, // WRITA
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/* 40 */
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{ &NOOP, REG_E|REG_D|REG_IX }, // VBLANK
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{ &NOOP, REG_E|REG_D|REG_B|REG_HL }, // BLANK
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{ &NOOP, REG_B|REG_C|REG_DE|REG_HL }, // SAVE
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{ &NOOP, REG_DE|REG_HL }, // RESTORE
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{ &NOOP, REG_B|REG_C|REG_DE|REG_HL }, // SCROLL
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/* 50 */
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{ &CHRDIS, REG_E|REG_D|REG_C|REG_A },
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{ &STRDIS, REG_E|REG_D|REG_C|REG_HL },
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{ &DISNUM, REG_E|REG_D|REG_C|REG_B|REG_HL },
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{ &NOOP, REG_DE|REG_A }, // RELABS
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{ &NOOP, REG_E|REG_D|REG_A }, // RELAB1
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/* 60 */
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{ &NOOP, REG_IX|REG_HL|REG_C }, // VECTC
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{ &NOOP, REG_IX|REG_HL }, // VECT
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{ &KCTASC, 0 },
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{ &SENTRY, REG_DE },
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{ &DOIT, REG_HL },
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/* 70 */
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{ &DOITB, REG_HL },
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{ &NOOP, 0 }, // PIZBRK
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{ &NOOP, REG_DE|REG_HL }, // MENU
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{ &NOOP, REG_BC|REG_HL }, // GETPAR
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{ &NOOP, REG_B|REG_C|REG_D|REG_E|REG_HL }, // GETNUM
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/* 80 */
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{ &PAWS, REG_B },
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{ &NOOP, REG_E|REG_D|REG_C }, // DISTIM
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{ &NOOP, REG_HL }, // INCSCR
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{ &INDEXN, REG_C|REG_HL }, // INDEXN
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{ &NOOP, REG_HL }, // STOREN
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/* 90 */
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{ &INDEXW, REG_A|REG_HL }, // INDEXW
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{ &INDEXB, REG_A|REG_HL }, // INDEXB
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{ &MOVE, REG_DE|REG_BC|REG_HL },
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{ &NOOP, 0 }, // SHIFTU
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{ &BCDADD, REG_DE|REG_B|REG_HL },
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/* 100 */
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{ &NOOP, 0 }, // BCDSUB
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{ &NOOP, 0 }, // BCDMUL
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{ &NOOP, 0 }, // BCDDIV
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{ &NOOP, 0 }, // BCDCHS
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{ &NOOP, 0 }, // BCDNEG
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/* 110 */
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{ &NOOP, 0 }, // DADD
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{ &NOOP, 0 }, // DSMG
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{ &NOOP, 0 }, // DABS
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{ &NOOP, 0 }, // NEGT
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{ &RANGED, REG_A },
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/* 120 */
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{ &NOOP, 0 }, // QUIT
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{ &NOOP, REG_A|REG_HL }, // SETB
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{ &NOOP, REG_DE|REG_HL }, // SETW
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{ &NOOP, REG_C|REG_DE|REG_HL }, // MSKTD
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};
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void SYSCALL(ContextBlock *ctx) {
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byte op = *ctx->params++;
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byte argmask;
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SysRoutine* routine;
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// user-defined?
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if (op & 0x80) {
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argmask = UMARGT[op>>1];
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routine = (SysRoutine*) USERTB[op>>1];
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} else {
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const SysCallEntry* entry = &SYSCALL_TABLE[op>>1];
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argmask = entry->argmask;
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routine = entry->routine;
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}
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// suck params into context block?
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if (op & 1) {
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suckParams(ctx, argmask);
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}
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// call the routine
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routine(ctx);
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}
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void bios_init() {
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ContextBlock ctx;
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memset((void*)0x4fce, 0, 0x5000-0x4fce);
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ACTINT(0);
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hw_verbl = 96*2;
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hw_horcb = 41;
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hw_inmod = 0x8;
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// call SENTRY once to set current values
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// (context block doesn't matter)
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SENTRY(&ctx);
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}
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