diff --git a/tools/emul/.gitignore b/tools/emul/.gitignore
index 2b9ca3c..3d1bbc7 100644
--- a/tools/emul/.gitignore
+++ b/tools/emul/.gitignore
@@ -8,3 +8,4 @@
 /cfsin/ed
 /cfsin/basic
 /cfsin/user.h
+*.o
diff --git a/tools/emul/Makefile b/tools/emul/Makefile
index 01daf6f..40fff0c 100644
--- a/tools/emul/Makefile
+++ b/tools/emul/Makefile
@@ -31,15 +31,18 @@ zasm/zasm-bin.h: zasm/zasm.bin
 
 shell/shell: shell/shell.c libz80/libz80.o shell/kernel-bin.h 
 bshell/shell: bshell/shell.c libz80/libz80.o bshell/shell-bin.h 
-$(ZASMBIN): zasm/zasm.c libz80/libz80.o zasm/kernel-bin.h zasm/zasm-bin.h $(CFSPACK)
+$(ZASMBIN): zasm/zasm.c emul.o libz80/libz80.o zasm/kernel-bin.h zasm/zasm-bin.h $(CFSPACK)
 runbin/runbin: runbin/runbin.c libz80/libz80.o
 $(TARGETS):
-	$(CC) $< libz80/libz80.o -o $@
+	$(CC) $< emul.o libz80/libz80.o -o $@
 
 libz80/libz80.o: libz80/z80.c
 	$(MAKE) -C libz80/codegen opcodes
 	$(CC) -Wall -ansi -g -c -o libz80/libz80.o libz80/z80.c
 
+emul.o: emul.c
+	$(CC) -c -o emul.o emul.c
+
 $(CFSPACK):
 	$(MAKE) -C ../cfspack
 
@@ -57,4 +60,4 @@ updatebootstrap: $(ZASMBIN) $(INCCFS)
 
 .PHONY: clean
 clean:
-	rm -f $(TARGETS) $(SHELLAPPS) zasm/*-bin.h shell/*-bin.h
+	rm -f $(TARGETS) $(SHELLAPPS) emul.o zasm/*-bin.h shell/*-bin.h
diff --git a/tools/emul/bshell/shell.c b/tools/emul/bshell/shell.c
index c49dce8..31df626 100644
--- a/tools/emul/bshell/shell.c
+++ b/tools/emul/bshell/shell.c
@@ -1,7 +1,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <termios.h>
-#include "../libz80/z80.h"
+#include "../emul.h"
 #include "shell-bin.h"
 
 /* Collapse OS shell with filesystem
@@ -39,8 +39,6 @@
 // 3 means incomplete addr setting
 #define FS_ADDR_PORT 0x02
 
-static Z80Context cpu;
-static uint8_t mem[0x10000] = {0};
 static uint8_t fsdev[MAX_FSDEV_SIZE] = {0};
 static uint32_t fsdev_size = 0;
 static uint32_t fsdev_ptr = 0;
@@ -48,105 +46,93 @@ static uint32_t fsdev_ptr = 0;
 static int  fsdev_addr_lvl = 0;
 static int running;
 
-static uint8_t io_read(int unused, uint16_t addr)
+static uint8_t iord_stdio()
 {
-    addr &= 0xff;
-    if (addr == STDIO_PORT) {
-        int c = getchar();
-        if (c == EOF) {
-            running = 0;
-        }
-        return (uint8_t)c;
-    } else if (addr == FS_DATA_PORT) {
-        if (fsdev_addr_lvl != 0) {
-            fprintf(stderr, "Reading FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
-            return 0;
-        }
-        if (fsdev_ptr < fsdev_size) {
+    int c = getchar();
+    if (c == EOF) {
+        running = 0;
+    }
+    return (uint8_t)c;
+}
+
+static uint8_t iord_fsdata()
+{
+    if (fsdev_addr_lvl != 0) {
+        fprintf(stderr, "Reading FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
+        return 0;
+    }
+    if (fsdev_ptr < fsdev_size) {
 #ifdef DEBUG
-            fprintf(stderr, "Reading FSDEV at offset %d\n", fsdev_ptr);
+        fprintf(stderr, "Reading FSDEV at offset %d\n", fsdev_ptr);
 #endif
-            return fsdev[fsdev_ptr];
-        } else {
-            // don't warn when ==, we're not out of bounds, just at the edge.
-            if (fsdev_ptr > fsdev_size) {
-                fprintf(stderr, "Out of bounds FSDEV read at %d\n", fsdev_ptr);
-            }
-            return 0;
-        }
-    } else if (addr == FS_ADDR_PORT) {
-        if (fsdev_addr_lvl != 0) {
-            return 3;
-        } else if (fsdev_ptr > fsdev_size) {
-            fprintf(stderr, "Out of bounds FSDEV addr request at %d / %d\n", fsdev_ptr, fsdev_size);
-            return 2;
-        } else if (fsdev_ptr == fsdev_size) {
-            return 1;
-        } else {
-            return 0;
-        }
+        return fsdev[fsdev_ptr];
     } else {
-        fprintf(stderr, "Out of bounds I/O read: %d\n", addr);
+        // don't warn when ==, we're not out of bounds, just at the edge.
+        if (fsdev_ptr > fsdev_size) {
+            fprintf(stderr, "Out of bounds FSDEV read at %d\n", fsdev_ptr);
+        }
         return 0;
     }
 }
 
-static void io_write(int unused, uint16_t addr, uint8_t val)
+static uint8_t iord_fsaddr()
 {
-    addr &= 0xff;
-    if (addr == STDIO_PORT) {
-        if (val == 0x04) { // CTRL+D
-            running = 0;
-        } else {
-            putchar(val);
-        }
-    } else if (addr == FS_DATA_PORT) {
-        if (fsdev_addr_lvl != 0) {
-            fprintf(stderr, "Writing to FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
-            return;
-        }
-        if (fsdev_ptr < fsdev_size) {
-#ifdef DEBUG
-            fprintf(stderr, "Writing to FSDEV (%d)\n", fsdev_ptr);
-#endif
-            fsdev[fsdev_ptr] = val;
-        } else if ((fsdev_ptr == fsdev_size) && (fsdev_ptr < MAX_FSDEV_SIZE)) {
-            // We're at the end of fsdev, grow it
-            fsdev[fsdev_ptr] = val;
-            fsdev_size++;
-#ifdef DEBUG
-            fprintf(stderr, "Growing FSDEV (%d)\n", fsdev_ptr);
-#endif
-        } else {
-            fprintf(stderr, "Out of bounds FSDEV write at %d\n", fsdev_ptr);
-        }
-    } else if (addr == FS_ADDR_PORT) {
-        if (fsdev_addr_lvl == 0) {
-            fsdev_ptr = val << 16;
-            fsdev_addr_lvl = 1;
-        } else if (fsdev_addr_lvl == 1) {
-            fsdev_ptr |= val << 8;
-            fsdev_addr_lvl = 2;
-        } else {
-            fsdev_ptr |= val;
-            fsdev_addr_lvl = 0;
-        }
+    if (fsdev_addr_lvl != 0) {
+        return 3;
+    } else if (fsdev_ptr > fsdev_size) {
+        fprintf(stderr, "Out of bounds FSDEV addr request at %d / %d\n", fsdev_ptr, fsdev_size);
+        return 2;
+    } else if (fsdev_ptr == fsdev_size) {
+        return 1;
     } else {
-        fprintf(stderr, "Out of bounds I/O write: %d / %d (0x%x)\n", addr, val, val);
+        return 0;
     }
 }
 
-static uint8_t mem_read(int unused, uint16_t addr)
+static void iowr_stdio(uint8_t val)
 {
-    return mem[addr];
+    if (val == 0x04) { // CTRL+D
+        running = 0;
+    } else {
+        putchar(val);
+    }
 }
 
-static void mem_write(int unused, uint16_t addr, uint8_t val)
+static void iowr_fsdata(uint8_t val)
 {
-    if (addr < RAMSTART) {
-        fprintf(stderr, "Writing to ROM (%d)!\n", addr);
+    if (fsdev_addr_lvl != 0) {
+        fprintf(stderr, "Writing to FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
+        return;
+    }
+    if (fsdev_ptr < fsdev_size) {
+#ifdef DEBUG
+        fprintf(stderr, "Writing to FSDEV (%d)\n", fsdev_ptr);
+#endif
+        fsdev[fsdev_ptr] = val;
+    } else if ((fsdev_ptr == fsdev_size) && (fsdev_ptr < MAX_FSDEV_SIZE)) {
+        // We're at the end of fsdev, grow it
+        fsdev[fsdev_ptr] = val;
+        fsdev_size++;
+#ifdef DEBUG
+        fprintf(stderr, "Growing FSDEV (%d)\n", fsdev_ptr);
+#endif
+    } else {
+        fprintf(stderr, "Out of bounds FSDEV write at %d\n", fsdev_ptr);
+    }
+}
+
+static void iowr_fsaddr(uint8_t val)
+{
+    if (fsdev_addr_lvl == 0) {
+        fsdev_ptr = val << 16;
+        fsdev_addr_lvl = 1;
+    } else if (fsdev_addr_lvl == 1) {
+        fsdev_ptr |= val << 8;
+        fsdev_addr_lvl = 2;
+    } else {
+        fsdev_ptr |= val;
+        fsdev_addr_lvl = 0;
     }
-    mem[addr] = val;
 }
 
 int main()
@@ -179,21 +165,22 @@ int main()
     tcsetattr(0, TCSAFLUSH, &termInfo);
 
 
+    Machine *m = emul_init();
+    m->ramstart = RAMSTART;
+    m->iord[STDIO_PORT] = iord_stdio;
+    m->iord[FS_DATA_PORT] = iord_fsdata;
+    m->iord[FS_ADDR_PORT] = iord_fsaddr;
+    m->iowr[STDIO_PORT] = iowr_stdio;
+    m->iowr[FS_DATA_PORT] = iowr_fsdata;
+    m->iowr[FS_ADDR_PORT] = iowr_fsaddr;
     // initialize memory
     for (int i=0; i<sizeof(KERNEL); i++) {
-        mem[i] = KERNEL[i];
+        m->mem[i] = KERNEL[i];
     }
     // Run!
     running = 1;
-    Z80RESET(&cpu);
-    cpu.ioRead = io_read;
-    cpu.ioWrite = io_write;
-    cpu.memRead = mem_read;
-    cpu.memWrite = mem_write;
 
-    while (running && !cpu.halted) {
-        Z80Execute(&cpu);
-    }
+    while (running && emul_step());
 
     printf("Done!\n");
     termInfo.c_lflag |= ECHO;
diff --git a/tools/emul/emul.c b/tools/emul/emul.c
new file mode 100644
index 0000000..d060123
--- /dev/null
+++ b/tools/emul/emul.c
@@ -0,0 +1,77 @@
+/* Common code between shell, zasm and runbin.
+
+They all run on the same kind of virtual machine: A z80 CPU, 64K of RAM/ROM.
+*/
+
+#include <string.h>
+#include "emul.h"
+
+static Machine m;
+
+static uint8_t io_read(int unused, uint16_t addr)
+{
+    addr &= 0xff;
+    IORD fn = m.iord[addr];
+    if (fn != NULL) {
+        return fn();
+    } else {
+        fprintf(stderr, "Out of bounds I/O read: %d\n", addr);
+        return 0;
+    }
+}
+
+static void io_write(int unused, uint16_t addr, uint8_t val)
+{
+    addr &= 0xff;
+    IOWR fn = m.iowr[addr];
+    if (fn != NULL) {
+        fn(val);
+    } else {
+        fprintf(stderr, "Out of bounds I/O write: %d / %d (0x%x)\n", addr, val, val);
+    }
+}
+
+static uint8_t mem_read(int unused, uint16_t addr)
+{
+    return m.mem[addr];
+}
+
+static void mem_write(int unused, uint16_t addr, uint8_t val)
+{
+    if (addr < m.ramstart) {
+        fprintf(stderr, "Writing to ROM (%d)!\n", addr);
+    }
+    m.mem[addr] = val;
+}
+
+Machine* emul_init()
+{
+    memset(m.mem, 0, 0x10000);
+    m.ramstart = 0;
+    for (int i=0; i<0x100; i++) {
+        m.iord[i] = NULL;
+        m.iowr[i] = NULL;
+    }
+    Z80RESET(&m.cpu);
+    m.cpu.memRead = mem_read;
+    m.cpu.memWrite = mem_write;
+    m.cpu.ioRead = io_read;
+    m.cpu.ioWrite = io_write;
+    return &m;
+}
+
+
+bool emul_step()
+{
+    if (!m.cpu.halted) {
+        Z80Execute(&m.cpu);
+        return true;
+    } else {
+        return false;
+    }
+}
+
+void emul_loop()
+{
+    while (emul_step());
+}
diff --git a/tools/emul/emul.h b/tools/emul/emul.h
new file mode 100644
index 0000000..61d2b8f
--- /dev/null
+++ b/tools/emul/emul.h
@@ -0,0 +1,22 @@
+#include <stdint.h>
+#include <stdbool.h>
+#include "libz80/z80.h"
+
+typedef uint8_t (*IORD) ();
+typedef void (*IOWR) (uint8_t data);
+
+typedef struct {
+    Z80Context cpu;
+    uint8_t mem[0x10000];
+    // Set to non-zero to specify where ROM ends. Any memory write attempt
+    // below ramstart will trigger a warning.
+    uint16_t ramstart;
+    // Array of 0x100 function pointers to IO read and write routines. Leave to
+    // NULL when IO port is unhandled.
+    IORD iord[0x100];
+    IOWR iowr[0x100];
+} Machine;
+
+Machine* emul_init();
+bool emul_step();
+void emul_loop();
diff --git a/tools/emul/runbin/runbin.c b/tools/emul/runbin/runbin.c
index c3d5947..2de5bb4 100644
--- a/tools/emul/runbin/runbin.c
+++ b/tools/emul/runbin/runbin.c
@@ -1,44 +1,19 @@
 #include <stdint.h>
 #include <stdio.h>
-#include "../libz80/z80.h"
+#include "../emul.h"
 
 /* runbin loads binary from stdin directly in memory address 0 then runs it
  * until it halts. The return code is the value of the register A at halt time.
  */
 
-static Z80Context cpu;
-static uint8_t mem[0x10000];
-
-static uint8_t io_read(int unused, uint16_t addr)
-{
-    addr &= 0xff;
-    fprintf(stderr, "Out of bounds I/O read: %d\n", addr);
-    return 0;
-}
-
-static void io_write(int unused, uint16_t addr, uint8_t val)
-{
-    addr &= 0xff;
-    fprintf(stderr, "Out of bounds I/O write: %d / %d\n", addr, val);
-}
-
-static uint8_t mem_read(int unused, uint16_t addr)
-{
-    return mem[addr];
-}
-
-static void mem_write(int unused, uint16_t addr, uint8_t val)
-{
-    mem[addr] = val;
-}
-
 int main()
 {
+    Machine *m = emul_init();
     // read stdin in mem
     int i = 0;
     int c = getchar();
     while (c != EOF) {
-        mem[i] = c & 0xff;
+        m->mem[i] = c & 0xff;
         i++;
         c = getchar();
     }
@@ -46,15 +21,7 @@ int main()
         fprintf(stderr, "No input, aborting\n");
         return 1;
     }
-    Z80RESET(&cpu);
-    cpu.ioRead = io_read;
-    cpu.ioWrite = io_write;
-    cpu.memRead = mem_read;
-    cpu.memWrite = mem_write;
-
-    while (!cpu.halted) {
-        Z80Execute(&cpu);
-    }
-    return cpu.R1.br.A;
+    emul_loop();
+    return m->cpu.R1.br.A;
 }
 
diff --git a/tools/emul/shell/shell.c b/tools/emul/shell/shell.c
index 6def224..cb74f2a 100644
--- a/tools/emul/shell/shell.c
+++ b/tools/emul/shell/shell.c
@@ -1,7 +1,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <termios.h>
-#include "../libz80/z80.h"
+#include "../emul.h"
 #include "kernel-bin.h"
 
 /* Collapse OS shell with filesystem
@@ -39,8 +39,6 @@
 // 3 means incomplete addr setting
 #define FS_ADDR_PORT 0x02
 
-static Z80Context cpu;
-static uint8_t mem[0x10000] = {0};
 static uint8_t fsdev[MAX_FSDEV_SIZE] = {0};
 static uint32_t fsdev_size = 0;
 static uint32_t fsdev_ptr = 0;
@@ -48,105 +46,93 @@ static uint32_t fsdev_ptr = 0;
 static int  fsdev_addr_lvl = 0;
 static int running;
 
-static uint8_t io_read(int unused, uint16_t addr)
+static uint8_t iord_stdio()
 {
-    addr &= 0xff;
-    if (addr == STDIO_PORT) {
-        int c = getchar();
-        if (c == EOF) {
-            running = 0;
-        }
-        return (uint8_t)c;
-    } else if (addr == FS_DATA_PORT) {
-        if (fsdev_addr_lvl != 0) {
-            fprintf(stderr, "Reading FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
-            return 0;
-        }
-        if (fsdev_ptr < fsdev_size) {
+    int c = getchar();
+    if (c == EOF) {
+        running = 0;
+    }
+    return (uint8_t)c;
+}
+
+static uint8_t iord_fsdata()
+{
+    if (fsdev_addr_lvl != 0) {
+        fprintf(stderr, "Reading FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
+        return 0;
+    }
+    if (fsdev_ptr < fsdev_size) {
 #ifdef DEBUG
-            fprintf(stderr, "Reading FSDEV at offset %d\n", fsdev_ptr);
+        fprintf(stderr, "Reading FSDEV at offset %d\n", fsdev_ptr);
 #endif
-            return fsdev[fsdev_ptr];
-        } else {
-            // don't warn when ==, we're not out of bounds, just at the edge.
-            if (fsdev_ptr > fsdev_size) {
-                fprintf(stderr, "Out of bounds FSDEV read at %d\n", fsdev_ptr);
-            }
-            return 0;
-        }
-    } else if (addr == FS_ADDR_PORT) {
-        if (fsdev_addr_lvl != 0) {
-            return 3;
-        } else if (fsdev_ptr > fsdev_size) {
-            fprintf(stderr, "Out of bounds FSDEV addr request at %d / %d\n", fsdev_ptr, fsdev_size);
-            return 2;
-        } else if (fsdev_ptr == fsdev_size) {
-            return 1;
-        } else {
-            return 0;
-        }
+        return fsdev[fsdev_ptr];
     } else {
-        fprintf(stderr, "Out of bounds I/O read: %d\n", addr);
+        // don't warn when ==, we're not out of bounds, just at the edge.
+        if (fsdev_ptr > fsdev_size) {
+            fprintf(stderr, "Out of bounds FSDEV read at %d\n", fsdev_ptr);
+        }
         return 0;
     }
 }
 
-static void io_write(int unused, uint16_t addr, uint8_t val)
+static uint8_t iord_fsaddr()
 {
-    addr &= 0xff;
-    if (addr == STDIO_PORT) {
-        if (val == 0x04) { // CTRL+D
-            running = 0;
-        } else {
-            putchar(val);
-        }
-    } else if (addr == FS_DATA_PORT) {
-        if (fsdev_addr_lvl != 0) {
-            fprintf(stderr, "Writing to FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
-            return;
-        }
-        if (fsdev_ptr < fsdev_size) {
-#ifdef DEBUG
-            fprintf(stderr, "Writing to FSDEV (%d)\n", fsdev_ptr);
-#endif
-            fsdev[fsdev_ptr] = val;
-        } else if ((fsdev_ptr == fsdev_size) && (fsdev_ptr < MAX_FSDEV_SIZE)) {
-            // We're at the end of fsdev, grow it
-            fsdev[fsdev_ptr] = val;
-            fsdev_size++;
-#ifdef DEBUG
-            fprintf(stderr, "Growing FSDEV (%d)\n", fsdev_ptr);
-#endif
-        } else {
-            fprintf(stderr, "Out of bounds FSDEV write at %d\n", fsdev_ptr);
-        }
-    } else if (addr == FS_ADDR_PORT) {
-        if (fsdev_addr_lvl == 0) {
-            fsdev_ptr = val << 16;
-            fsdev_addr_lvl = 1;
-        } else if (fsdev_addr_lvl == 1) {
-            fsdev_ptr |= val << 8;
-            fsdev_addr_lvl = 2;
-        } else {
-            fsdev_ptr |= val;
-            fsdev_addr_lvl = 0;
-        }
+    if (fsdev_addr_lvl != 0) {
+        return 3;
+    } else if (fsdev_ptr > fsdev_size) {
+        fprintf(stderr, "Out of bounds FSDEV addr request at %d / %d\n", fsdev_ptr, fsdev_size);
+        return 2;
+    } else if (fsdev_ptr == fsdev_size) {
+        return 1;
     } else {
-        fprintf(stderr, "Out of bounds I/O write: %d / %d (0x%x)\n", addr, val, val);
+        return 0;
     }
 }
 
-static uint8_t mem_read(int unused, uint16_t addr)
+static void iowr_stdio(uint8_t val)
 {
-    return mem[addr];
+    if (val == 0x04) { // CTRL+D
+        running = 0;
+    } else {
+        putchar(val);
+    }
 }
 
-static void mem_write(int unused, uint16_t addr, uint8_t val)
+static void iowr_fsdata(uint8_t val)
 {
-    if (addr < RAMSTART) {
-        fprintf(stderr, "Writing to ROM (%d)!\n", addr);
+    if (fsdev_addr_lvl != 0) {
+        fprintf(stderr, "Writing to FSDEV in the middle of an addr op (%d)\n", fsdev_ptr);
+        return;
+    }
+    if (fsdev_ptr < fsdev_size) {
+#ifdef DEBUG
+        fprintf(stderr, "Writing to FSDEV (%d)\n", fsdev_ptr);
+#endif
+        fsdev[fsdev_ptr] = val;
+    } else if ((fsdev_ptr == fsdev_size) && (fsdev_ptr < MAX_FSDEV_SIZE)) {
+        // We're at the end of fsdev, grow it
+        fsdev[fsdev_ptr] = val;
+        fsdev_size++;
+#ifdef DEBUG
+        fprintf(stderr, "Growing FSDEV (%d)\n", fsdev_ptr);
+#endif
+    } else {
+        fprintf(stderr, "Out of bounds FSDEV write at %d\n", fsdev_ptr);
+    }
+}
+
+static void iowr_fsaddr(uint8_t val)
+{
+    if (fsdev_addr_lvl == 0) {
+        fsdev_ptr = val << 16;
+        fsdev_addr_lvl = 1;
+    } else if (fsdev_addr_lvl == 1) {
+        fsdev_ptr |= val << 8;
+        fsdev_addr_lvl = 2;
+    } else {
+        fsdev_ptr |= val;
+        fsdev_addr_lvl = 0;
     }
-    mem[addr] = val;
 }
 
 int main()
@@ -179,21 +165,22 @@ int main()
     tcsetattr(0, TCSAFLUSH, &termInfo);
 
 
+    Machine *m = emul_init();
+    m->ramstart = RAMSTART;
+    m->iord[STDIO_PORT] = iord_stdio;
+    m->iord[FS_DATA_PORT] = iord_fsdata;
+    m->iord[FS_ADDR_PORT] = iord_fsaddr;
+    m->iowr[STDIO_PORT] = iowr_stdio;
+    m->iowr[FS_DATA_PORT] = iowr_fsdata;
+    m->iowr[FS_ADDR_PORT] = iowr_fsaddr;
     // initialize memory
     for (int i=0; i<sizeof(KERNEL); i++) {
-        mem[i] = KERNEL[i];
+        m->mem[i] = KERNEL[i];
     }
     // Run!
     running = 1;
-    Z80RESET(&cpu);
-    cpu.ioRead = io_read;
-    cpu.ioWrite = io_write;
-    cpu.memRead = mem_read;
-    cpu.memWrite = mem_write;
 
-    while (running && !cpu.halted) {
-        Z80Execute(&cpu);
-    }
+    while (running && emul_step());
 
     printf("Done!\n");
     termInfo.c_lflag |= ECHO;
diff --git a/tools/emul/zasm/zasm.c b/tools/emul/zasm/zasm.c
index bb3cf04..af3309c 100644
--- a/tools/emul/zasm/zasm.c
+++ b/tools/emul/zasm/zasm.c
@@ -1,7 +1,7 @@
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>
-#include "../libz80/z80.h"
+#include "../emul.h"
 #include "kernel-bin.h"
 #include "zasm-bin.h"
 
@@ -48,8 +48,6 @@
 // you want to spit this content to stderr.
 //#define VERBOSE
 
-static Z80Context cpu;
-static uint8_t mem[0x10000];
 // STDIN buffer, allows us to seek and tell
 static uint8_t inpt[STDIN_BUFSIZE];
 static int inpt_size;
@@ -61,100 +59,100 @@ static uint32_t fsdev_size = 0;
 static uint32_t fsdev_ptr = 0;
 static uint8_t fsdev_seek_tell_cnt = 0;
 
-static uint8_t io_read(int unused, uint16_t addr)
+static uint8_t iord_stdio()
 {
-    addr &= 0xff;
-    if (addr == STDIO_PORT) {
-        if (inpt_ptr < inpt_size) {
-            return inpt[inpt_ptr++];
-        } else {
-            return 0;
-        }
-    } else if (addr == STDIN_SEEK_PORT) {
-        if (middle_of_seek_tell) {
-            middle_of_seek_tell = 0;
-            return inpt_ptr & 0xff;
-        } else {
-#ifdef DEBUG
-            fprintf(stderr, "tell %d\n", inpt_ptr);
-#endif
-            middle_of_seek_tell = 1;
-            return inpt_ptr >> 8;
-        }
-    } else if (addr == FS_DATA_PORT) {
-        if (fsdev_ptr < fsdev_size) {
-            return fsdev[fsdev_ptr++];
-        } else {
-            return 0;
-        }
-    } else if (addr == FS_SEEK_PORT) {
-        if (fsdev_seek_tell_cnt != 0) {
-            return fsdev_seek_tell_cnt;
-        } else if (fsdev_ptr >= fsdev_size) {
-            return 1;
-        } else {
-            return 0;
-        }
+    if (inpt_ptr < inpt_size) {
+        return inpt[inpt_ptr++];
     } else {
-        fprintf(stderr, "Out of bounds I/O read: %d\n", addr);
         return 0;
     }
 }
 
-static void io_write(int unused, uint16_t addr, uint8_t val)
+static uint8_t iord_stdin_seek()
 {
-    addr &= 0xff;
-    if (addr == STDIO_PORT) {
-// When mem-dumping, we don't output regular stuff.
-#ifndef MEMDUMP
-        putchar(val);
-#endif
-    } else if (addr == STDIN_SEEK_PORT) {
-        if (middle_of_seek_tell) {
-            inpt_ptr |= val;
-            middle_of_seek_tell = 0;
-#ifdef DEBUG
-            fprintf(stderr, "seek %d\n", inpt_ptr);
-#endif
-        } else {
-            inpt_ptr = (val << 8) & 0xff00;
-            middle_of_seek_tell = 1;
-        }
-    } else if (addr == FS_DATA_PORT) {
-        if (fsdev_ptr < fsdev_size) {
-            fsdev[fsdev_ptr++] = val;
-        }
-    } else if (addr == FS_SEEK_PORT) {
-        if (fsdev_seek_tell_cnt == 0) {
-            fsdev_ptr = val << 16;
-            fsdev_seek_tell_cnt = 1;
-        } else if (fsdev_seek_tell_cnt == 1) {
-            fsdev_ptr |= val << 8;
-            fsdev_seek_tell_cnt = 2;
-        } else {
-            fsdev_ptr |= val;
-            fsdev_seek_tell_cnt = 0;
-#ifdef DEBUG
-            fprintf(stderr, "FS seek %d\n", fsdev_ptr);
-#endif
-        }
-    } else if (addr == STDERR_PORT) {
-#ifdef VERBOSE
-        fputc(val, stderr);
-#endif
+    if (middle_of_seek_tell) {
+        middle_of_seek_tell = 0;
+        return inpt_ptr & 0xff;
     } else {
-        fprintf(stderr, "Out of bounds I/O write: %d / %d (0x%x)\n", addr, val, val);
+#ifdef DEBUG
+        fprintf(stderr, "tell %d\n", inpt_ptr);
+#endif
+        middle_of_seek_tell = 1;
+        return inpt_ptr >> 8;
     }
 }
 
-static uint8_t mem_read(int unused, uint16_t addr)
+static uint8_t iord_fsdata()
 {
-    return mem[addr];
+    if (fsdev_ptr < fsdev_size) {
+        return fsdev[fsdev_ptr++];
+    } else {
+        return 0;
+    }
 }
 
-static void mem_write(int unused, uint16_t addr, uint8_t val)
+static uint8_t iord_fsseek()
 {
-    mem[addr] = val;
+    if (fsdev_seek_tell_cnt != 0) {
+        return fsdev_seek_tell_cnt;
+    } else if (fsdev_ptr >= fsdev_size) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+static void iowr_stdio(uint8_t val)
+{
+// When mem-dumping, we don't output regular stuff.
+#ifndef MEMDUMP
+    putchar(val);
+#endif
+}
+
+static void iowr_stdin_seek(uint8_t val)
+{
+    if (middle_of_seek_tell) {
+        inpt_ptr |= val;
+        middle_of_seek_tell = 0;
+#ifdef DEBUG
+        fprintf(stderr, "seek %d\n", inpt_ptr);
+#endif
+    } else {
+        inpt_ptr = (val << 8) & 0xff00;
+        middle_of_seek_tell = 1;
+    }
+}
+
+static void iowr_fsdata(uint8_t val)
+{
+    if (fsdev_ptr < fsdev_size) {
+        fsdev[fsdev_ptr++] = val;
+    }
+}
+
+static void iowr_fsseek(uint8_t val)
+{
+    if (fsdev_seek_tell_cnt == 0) {
+        fsdev_ptr = val << 16;
+        fsdev_seek_tell_cnt = 1;
+    } else if (fsdev_seek_tell_cnt == 1) {
+        fsdev_ptr |= val << 8;
+        fsdev_seek_tell_cnt = 2;
+    } else {
+        fsdev_ptr |= val;
+        fsdev_seek_tell_cnt = 0;
+#ifdef DEBUG
+        fprintf(stderr, "FS seek %d\n", fsdev_ptr);
+#endif
+    }
+}
+
+static void iowr_stderr(uint8_t val)
+{
+#ifdef VERBOSE
+    fputc(val, stderr);
+#endif
 }
 
 int main(int argc, char *argv[])
@@ -163,12 +161,22 @@ int main(int argc, char *argv[])
         fprintf(stderr, "Too many args\n");
         return 1;
     }
+    Machine *m = emul_init();
+    m->iord[STDIO_PORT] = iord_stdio;
+    m->iord[STDIN_SEEK_PORT] = iord_stdin_seek;
+    m->iord[FS_DATA_PORT] = iord_fsdata;
+    m->iord[FS_SEEK_PORT] = iord_fsseek;
+    m->iowr[STDIO_PORT] = iowr_stdio;
+    m->iowr[STDIN_SEEK_PORT] = iowr_stdin_seek;
+    m->iowr[FS_DATA_PORT] = iowr_fsdata;
+    m->iowr[FS_SEEK_PORT] = iowr_fsseek;
+    m->iowr[STDERR_PORT] = iowr_stderr;
     // initialize memory
     for (int i=0; i<sizeof(KERNEL); i++) {
-        mem[i] = KERNEL[i];
+        m->mem[i] = KERNEL[i];
     }
     for (int i=0; i<sizeof(USERSPACE); i++) {
-        mem[i+USER_CODE] = USERSPACE[i];
+        m->mem[i+USER_CODE] = USERSPACE[i];
     }
     char *init_org = "00";
     if (argc >= 2) {
@@ -178,8 +186,8 @@ int main(int argc, char *argv[])
         }
     }
     // glue.asm knows that it needs to fetch these arguments at this address.
-    mem[0xff00] = init_org[0];
-    mem[0xff01] = init_org[1];
+    m->mem[0xff00] = init_org[0];
+    m->mem[0xff01] = init_org[1];
     fsdev_size = 0;
     if (argc == 3) {
         FILE *fp = fopen(argv[2], "r");
@@ -209,25 +217,18 @@ int main(int argc, char *argv[])
     }
     inpt_size = inpt_ptr;
     inpt_ptr = 0;
-    Z80RESET(&cpu);
-    cpu.ioRead = io_read;
-    cpu.ioWrite = io_write;
-    cpu.memRead = mem_read;
-    cpu.memWrite = mem_write;
 
-    while (!cpu.halted) {
-        Z80Execute(&cpu);
-    }
+    emul_loop();
 #ifdef MEMDUMP
     for (int i=0; i<0x10000; i++) {
         putchar(mem[i]);
     }
 #endif
     fflush(stdout);
-    int res = cpu.R1.br.A;
+    int res = m->cpu.R1.br.A;
     if (res != 0) {
-        int lineno = cpu.R1.wr.HL;
-        int inclineno = cpu.R1.wr.DE;
+        int lineno = m->cpu.R1.wr.HL;
+        int inclineno = m->cpu.R1.wr.DE;
         if (inclineno) {
             fprintf(
                 stderr,