More i8080 + NEC changes (#18)

* More i8080 changes * Fix compilation * More foundational i8080 work * Switch to __builtin_parity for parity flag setting Fix some incorrectly implemented instructions
2026-02-25 21:43:16 -07:00 · 2022-09-10 14:50:50 +06:00
parent 176278bca0
commit fc2fac4c73
4 changed files with 173 additions and 31 deletions
--- a/src/cpu/8080.c
+++ b/src/cpu/8080.c
@@ -15,6 +15,151 @@


 #include <stdint.h>
+#include <stdlib.h>
+#include "cpu.h"
+#include <86box/timer.h>
 #include <86box/i8080.h>
+#include <86box/mem.h>
+
+static int prefetching = 1, completed = 1;
+static int in_rep = 0, repeating = 0, rep_c_flag = 0;
+static int oldc, clear_lock = 0;
+static int refresh = 0, cycdiff;
+
+static void
+clock_start(void)
+{
+    cycdiff = cycles;
+}
+
+
+static void
+clock_end(void)
+{
+    int diff = cycdiff - cycles;
+
+    /* On 808x systems, clock speed is usually crystal frequency divided by an integer. */
+    tsc += (uint64_t)diff * ((uint64_t)xt_cpu_multi >> 32ULL);		/* Shift xt_cpu_multi by 32 bits to the right and then multiply. */
+    if (TIMER_VAL_LESS_THAN_VAL(timer_target, (uint32_t)tsc))
+	timer_process();
+}
+
+static void
+wait(int c, int bus)
+{
+    cycles -= c;
+    if (bus < 2) {
+	    clock_end();
+	    clock_start();
+    }
+}
+
+static uint8_t
+readmemb(uint32_t a)
+{
+    uint8_t ret;
+
+    wait(4, 1);
+    ret = read_mem_b(a);
+
+    return ret;
+}
+
+static uint8_t
+ins_fetch(i8080* cpu)
+{
+    uint8_t ret = readmemb(cpu->pmembase + cpu->pc);
+
+    cpu->pc++;
+    return ret;
+}
+
+void
+transfer_from_808x(i8080* cpu)
+{
+    cpu->hl = BX;
+    cpu->bc = CX;
+    cpu->de = DX;
+    cpu->a = AL;
+    cpu->flags = cpu_state.flags & 0xFF;
+    cpu->sp = BP;
+    cpu->pc = cpu_state.pc;
+    cpu->oldpc = cpu_state.oldpc;
+    cpu->pmembase = cs;
+    cpu->dmembase = ds;
+}
+
+void
+transfer_to_808x(i8080* cpu)
+{
+    BX = cpu->hl;
+    CX = cpu->bc;
+    DX = cpu->de;
+    AL = cpu->a;
+    cpu_state.flags &= 0xFF00;
+    cpu_state.flags |= cpu->flags & 0xFF;
+    BP = cpu->sp;
+    cpu_state.pc = cpu->pc;
+}
+
+uint8_t
+getreg_i8080(i8080 *cpu, uint8_t reg)
+{
+    uint8_t ret = 0xFF;
+    switch(reg)
+    {
+        case 0x0: ret = cpu->b; break;
+        case 0x1: ret = cpu->c; break;
+        case 0x2: ret = cpu->d; break;
+        case 0x3: ret = cpu->e; break;
+        case 0x4: ret = cpu->h; break;
+        case 0x5: ret = cpu->l; break;
+        case 0x6: ret = readmemb(cpu->dmembase + cpu->sp); break;
+        case 0x7: ret = cpu->a; break;
+    }
+    return ret;
+}
+
+void
+interpret_exec8080(i8080* cpu, uint8_t opcode, uint8_t (*fetch_instruction)(i8080*))
+{
+    switch (opcode) {
+        case 0x00:
+        {
+            break;
+        }
+    }
+}

 /* Actually implement i8080 emulation. */
+void
+exec8080(i8080* cpu, int cycs)
+{
+    uint8_t temp = 0, temp2;
+    uint8_t old_af;
+	uint8_t handled = 0;
+    uint16_t addr, tempw;
+    uint16_t new_ip;
+    int bits;
+
+    cycles += cycs;
+
+    while (cycles > 0) {
+        clock_start();
+
+        if (!repeating) {
+            cpu->oldpc = cpu->pc;
+            opcode = ins_fetch(cpu);
+            oldc = cpu->flags & C_FLAG_I8080;
+            wait(1, 0);
+        }
+        completed = 1;
+        if (completed) {
+            repeating = 0;
+            in_rep = 0;
+            rep_c_flag = 0;
+            clock_end();
+            //check_interrupts();
+        }
+    }
+}