Add stubbed EMC (emulator call) instruction

Makefile

@@ -32,17 +32,19 @@ disass: bin/disass.o bin/vm.o
 bin/%.o: src/%.c
 	$(CC) $(CFLAGS) -o $@ -c $^
 
+bin/emcalls.o:
 bin/vm.o:
 bin/main.o:
 bin/disass.o:
 
+# needs to be run separately
 rom: rom.bin
 	xxd -i src/$^ > src/$@.h
 
 rom.bin: src/rom.asm src/zeropage.incbin
 	./ass.sh src/rom.asm src/zeropage.incbin
 
-$(TARGET): bin/main.o bin/vm.o
+$(TARGET): bin/main.o bin/vm.o bin/emcalls.o
 	$(CC) $(CFLAGS) -o bin/$@$(TRACE_SUFFIX) $^
 
 clean:

ass.sh

@@ -37,6 +37,7 @@ bad_assemble() {
     sed -i 's/JMP[[:blank:]]/0d/gi' "$1"
     sed -i 's/BEQ[[:blank:]]/0e/gi' "$1"
     sed -i 's/BNQ[[:blank:]]/0f/gi' "$1"
+    sed -i 's/EMC[[:blank:]]/10/gi' "$1"
     sed -i 's/NOP[[:blank:]]*/ff 00 00/gi' "$1"
 
     sed -i 's/H//gi' "$1"  # remove hex suffix 'h' after only hex digits remain

src/disass.c

@@ -1,3 +1,5 @@
+/* x1phosura 2021 */
+
 #include <assert.h>
 #include <getopt.h>
 #include <stdbool.h>

src/emcalls.c

@@ -0,0 +1,34 @@
+/* emcalls.c: This file implements emulator calls ("emcalls"). Emcalls are
+analogous to system calls, except since there's no real OS, they're handled
+directly by the emulator. The basic usage should revolve around adding cases
+to the emcall switch-case, where each case is a special emcall that calls a
+function to handle it. This is perhaps the easiest way to plug fancy features
+into the emulator itself; basically treat the EMC instruction is like the ioctl
+syscall (_now_ I see why ioctl is such a tempting serpent of a syscall to have)
+
+x1phosura 2021
+*/
+
+#include <stdint.h>
+#include <stdio.h>
+
+
+void do_emcall(uint8_t emc_args[2])
+{
+	// emc_args[1] may be used in the future
+	switch(emc_args[0]) {
+	case 0x00:
+		printf("I'm a zero emcall!\n"); // replace with emcall handler
+		break;
+	case 0x01:
+		printf("I'm a one emcall!\n"); // replace with emcall handler
+		break;
+	case 0x02:
+		printf("I'm a two emcall!\n"); // replace with emcall handler
+		break;
+	default:
+		printf("EMC: 1st arg: 0x%02x, 2nd arg: 0x%02x\n", emc_args[0], emc_args[1]);
+	}
+	printf("[DEBUG] TODO: finish (stubbed)\n");
+}
+

src/emcalls.h

@@ -0,0 +1,6 @@
+/* x1phosura 2021 */
+
+#pragma once                    // WAAAAAY better than a dumb header guard ;)
+
+void do_emcall(uint8_t emc_args[2]);
+

src/main.c

@@ -1,3 +1,5 @@
+/* x1phosura 2021 */
+
 #include <assert.h>
 #include <stdbool.h>
 #include <stdint.h>

src/rom.asm

@@ -419,7 +419,7 @@ push  0x400b    # check fourth block
 pushi 0x1d00
 push  0x410b
 pushi 0x1600
-0xee 0x07 0x30  # junk NOP
+emc   0x0122
 0x30 0x30 0x30  # junk NOP
 push  0x420b
 pushi 0x4400
@@ -431,7 +431,7 @@ bnq   0xd102    # Fail if any two bytes ever not equal
 pop   0xffff
 pop   0xffff
 0xee 0x07 0x30  # junk NOP
-0xee 0x07 0x30  # junk NOP
+emc   0x3344
 bnq   0xd102    # Fail if any two bytes ever not equal
 pop   0xffff
 0xee 0x07 0x30  # junk NOP

src/rom.h

@@ -85,10 +85,10 @@ unsigned char src_rom_bin[] = {
   0x30, 0x02, 0xff, 0xff, 0x02, 0xff, 0xff, 0x0f, 0xd1, 0x02, 0x02, 0xff,
   0xff, 0xee, 0x07, 0x30, 0x02, 0xff, 0xff, 0x0f, 0xd1, 0x02, 0x02, 0xff,
   0xff, 0x02, 0xff, 0xff, 0x01, 0x40, 0x0b, 0x03, 0x1d, 0x00, 0x01, 0x41,
-  0x0b, 0x03, 0x16, 0x00, 0xee, 0x07, 0x30, 0x30, 0x30, 0x30, 0x01, 0x42,
+  0x0b, 0x03, 0x16, 0x00, 0x10, 0x01, 0x22, 0x30, 0x30, 0x30, 0x01, 0x42,
   0x0b, 0x03, 0x44, 0x00, 0x01, 0x43, 0x0b, 0x03, 0x75, 0x00, 0x0f, 0xd1,
-  0x02, 0x02, 0xff, 0xff, 0x02, 0xff, 0xff, 0xee, 0x07, 0x30, 0xee, 0x07,
-  0x30, 0x0f, 0xd1, 0x02, 0x02, 0xff, 0xff, 0xee, 0x07, 0x30, 0x02, 0xff,
+  0x02, 0x02, 0xff, 0xff, 0x02, 0xff, 0xff, 0xee, 0x07, 0x30, 0x10, 0x33,
+  0x44, 0x0f, 0xd1, 0x02, 0x02, 0xff, 0xff, 0xee, 0x07, 0x30, 0x02, 0xff,
   0xff, 0x0f, 0xd1, 0x02, 0x02, 0xff, 0xff, 0x02, 0xff, 0xff, 0xee, 0x07,
   0x30, 0x0f, 0xd1, 0x02, 0x02, 0xff, 0xff, 0x30, 0x30, 0x30, 0x02, 0xff,
   0xff, 0x0d, 0xcb, 0x02, 0x01, 0xcb, 0x02, 0x40, 0x77, 0x12, 0x00, 0x00,

src/vm.c

@@ -23,6 +23,7 @@ use assert()s to make sure pc, sp, etc... are valid
 #endif
 
 #include "vm.h"
+#include "emcalls.h"
 
 
 #ifdef TRACE    // TRACE_VARS
@@ -50,7 +51,6 @@ static inline void push(struct CPU *cpu, uint8_t val)
 		++cpu->sp;
 }
 
-
 static inline uint8_t pop(struct CPU *cpu)
 {
 	uint8_t val;
@@ -62,7 +62,6 @@ static inline uint8_t pop(struct CPU *cpu)
 	return val;
 }
 
-
 /* vm_do_instruction:
  */
 uint16_t vm_do_instruction(struct CPU *cpu, uint8_t *mem, uint8_t instr[3])
@@ -163,6 +162,10 @@ uint16_t vm_do_instruction(struct CPU *cpu, uint8_t *mem, uint8_t instr[3])
 				return operand;
 		pc += 3;
 		break;
+	case EMC:
+		do_emcall(operands);
+		pc += 3;
+		break;
 	case NOP:
 		pc += 3;
 		break;
@@ -208,6 +211,7 @@ void print_op_decoded(uint8_t i[3], bool pargs)
 	case JMP:   printf("JMP"); if (pargs) printf(fmt, i[1], i[2]); break;
 	case BEQ:   printf("BEQ"); if (pargs) printf(fmt, i[1], i[2]); break;
 	case BNQ:   printf("BNQ"); if (pargs) printf(fmt, i[1], i[2]); break;
+	case EMC:   printf("EMC"); if (pargs) printf(fmt, i[1], i[2]); break;
 	case NOP:   printf("NOP"); break;
 	default:    printf("0x%02x 0x%02x 0x%02x", i[0], i[1], i[2]);
 	}

src/vm.h

@@ -23,6 +23,7 @@ enum instructions {
 	JMP   = 13,
 	BEQ   = 14,
 	BNQ   = 15,
+	EMC   = 16,
 	// every opcode 0x10-0xfe is basically just a NOP just to be annoying
 	NOP = 0xff
 };