117 lines
3.0 KiB
C
117 lines
3.0 KiB
C
/* This file is included into vb.c and cannot be compiled on its own. */
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#ifdef VBAPI
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/***************************** Library Functions *****************************/
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/* Process component */
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static void padEmulate(VB *sim, uint32_t clocks) {
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/* No hardware read in progress */
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if (sim->pad.si_stat == 0)
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return;
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/* Hardware read completes after time to process */
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if (sim->pad.si_stat > clocks) {
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sim->pad.si_stat -= clocks;
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return;
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}
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/* Complete hardware read */
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sim->pad.si_stat = 0;
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sim->pad.sdlr = sim->pad.keys;
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sim->pad.sdhr = sim->pad.keys >> 8;
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/* Raise game pad interrupt */
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if (
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!sim->pad.k_int_inh &&
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(sim->pad.keys & 0xFFF0) != 0 &&
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(sim->pad.keys & 0x000E) == 0
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) sim->cpu.irq |= 0x0001;
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}
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/* Read a value from SCR */
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static int32_t padReadControl(VB *sim) {
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return 0x4C |
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sim->pad.k_int_inh << 7 |
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sim->pad.para_si << 5 |
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sim->pad.soft_ck << 4 |
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!!sim->pad.si_stat << 1 |
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sim->pad.s_abt_dis
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;
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}
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/* Simulate a hardware reset */
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static void padReset(VB *sim) {
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/* Normal */
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sim->pad.k_int_inh = 0;
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sim->pad.para_si = 0;
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sim->pad.s_abt_dis = 0;
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sim->pad.sdhr = 0x00;
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sim->pad.sdlr = 0x00;
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sim->pad.si_stat = 0;
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sim->pad.soft_ck = 0;
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/* Other */
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sim->pad.step = 0;
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}
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/* Write a value to SCR */
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static void padWriteControl(VB *sim, uint8_t value) {
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/* Acknowledge and disable interrupt */
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sim->pad.k_int_inh = value >> 7 & 1;
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if (sim->pad.k_int_inh)
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sim->cpu.irq &= ~0x0001;
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/* Enable or disable hardware reads */
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sim->pad.s_abt_dis = value & 1;
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if (sim->pad.s_abt_dis)
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sim->pad.si_stat = 0; /* Abort hardware read */
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/* Initiate a hardware read */
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if (
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(value & 0x04) && /* HW-SI */
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sim->pad.si_stat == 0 && /* No hardware read underway */
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!sim->pad.s_abt_dis /* Hardware reads enabled */
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) {
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sim->pad.si_stat = 10240; /* 512us */
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sim->pad.step = 0; /* Abort software read */
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}
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/* Reset the read operation */
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sim->pad.para_si = value >> 5 & 1;
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if (
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sim->pad.para_si &&
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sim->pad.si_stat == 0 /* No hardware read underway */
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) sim->pad.step = 32;
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/* Signal a bit for a software read */
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sim->pad.soft_ck = value >> 4 & 1;
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if (
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sim->pad.step != 0 && /* Software read is underway */
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!sim->pad.para_si && /* Not resetting software read */
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((sim->pad.soft_ck ^ sim->pad.step) & 1) == 1 /* Advance */
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) {
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sim->pad.step--;
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if (sim->pad.step == 0) {
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sim->pad.sdlr = sim->pad.keys;
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sim->pad.sdhr = sim->pad.keys >> 8;
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}
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}
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}
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/* Determine how many clocks are guaranteed to process */
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static uint32_t padUntil(VB *sim, uint32_t clocks) {
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return sim->pad.si_stat != 0 && sim->pad.si_stat < clocks ?
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sim->pad.si_stat : clocks;
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}
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#endif /* VBAPI */
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