Implement game pad and timer

2024-10-19 20:35:56 -05:00
parent 37b9a94338
commit e9f5437c1f
6 changed files with 386 additions and 9 deletions
@@ -0,0 +1,117 @@
+/* This file is included into vb.c and cannot be compiled on its own. */
+#ifdef VBAPI
+
+
+
+/***************************** Library Functions *****************************/
+
+/* Process component */
+static int padEmulate(VB *sim, uint32_t clocks) {
+
+    /* No hardware read in progress */
+    if (sim->pad.si_stat == 0)
+        return 0;
+
+    /* Hardware read completes after time to process */
+    if (sim->pad.si_stat > clocks) {
+        sim->pad.si_stat -= clocks;
+        return 0;
+    }
+
+    /* Complete hardware read */
+    sim->pad.si_stat = 0;
+    sim->pad.sdlr    = sim->pad.keys;
+    sim->pad.sdhr    = sim->pad.keys >> 8;
+
+    /* Raise game pad interrupt */
+    if (
+        !sim->pad.k_int_inh           &&
+        (sim->pad.keys & 0xFFF0) != 0 &&
+        (sim->pad.keys & 0x000E) == 0
+    ) sim->cpu.irq |= 0x0001;
+
+    return 0;
+}
+
+/* Read a value from SCR */
+static int32_t padReadControl(VB *sim) {
+    return 0x4C |
+        sim->pad.k_int_inh << 7 |
+        sim->pad.para_si   << 5 |
+        sim->pad.soft_ck   << 4 |
+        !!sim->pad.si_stat << 1 |
+        sim->pad.s_abt_dis
+    ;
+}
+
+/* Simulate a hardware reset */
+static void padReset(VB *sim) {
+
+    /* Normal */
+    sim->pad.k_int_inh = 0;
+    sim->pad.para_si   = 0;
+    sim->pad.s_abt_dis = 0;
+    sim->pad.sdhr      = 0x00;
+    sim->pad.sdlr      = 0x00;
+    sim->pad.si_stat   = 0;
+    sim->pad.soft_ck   = 0;
+
+    /* Other */
+    sim->pad.step = 0;
+}
+
+/* Write a value to SCR */
+static void padWriteControl(VB *sim, uint8_t value) {
+
+    /* Acknowledge and disable interrupt */
+    sim->pad.k_int_inh = value >> 7 & 1;
+    if (sim->pad.k_int_inh)
+        sim->cpu.irq &= ~0x0001;
+
+    /* Enable or disable hardware reads */
+    sim->pad.s_abt_dis = value & 1;
+    if (sim->pad.s_abt_dis)
+        sim->pad.si_stat = 0; /* Abort hardware read */
+
+    /* Initiate a hardware read */
+    if (
+        (value & 0x04)        && /* HW-SI */
+        sim->pad.si_stat == 0 && /* No hardware read underway */
+        !sim->pad.s_abt_dis      /* Hardware reads enabled */
+    ) {
+        sim->pad.si_stat = 10240; /* 512us */
+        sim->pad.step    = 0;     /* Abort software read */
+    }
+
+    /* Reset the read operation */
+    sim->pad.para_si = value >> 5 & 1;
+    if (
+        sim->pad.para_si &&
+        sim->pad.si_stat == 0 /* No hardware read underway */
+    ) sim->pad.step = 32;
+
+    /* Signal a bit for a software read */
+    sim->pad.soft_ck = value >> 4 & 1;
+    if (
+        sim->pad.step != 0 && /* Software read is underway */
+        !sim->pad.para_si  && /* Not resetting software read */
+        ((sim->pad.soft_ck ^ sim->pad.step) & 1) == 1 /* Advance */
+    ) {
+        sim->pad.step--;
+        if (sim->pad.step == 0) {
+            sim->pad.sdlr = sim->pad.keys;
+            sim->pad.sdhr = sim->pad.keys >> 8;
+        }
+    }
+
+}
+
+/* Determine how many clocks are guaranteed to process */
+static uint32_t padUntil(VB *sim, uint32_t clocks) {
+    return sim->pad.si_stat != 0 && sim->pad.si_stat < clocks ?
+        sim->pad.si_stat : clocks;
+}
+
+
+
+#endif /* VBAPI */