diff --git a/tools/emul/.gitignore b/tools/emul/.gitignore
index ca936d9..b485ee4 100644
--- a/tools/emul/.gitignore
+++ b/tools/emul/.gitignore
@@ -1,5 +1,6 @@
 /shell
 /zasm
+/zasm-includes.h
 /*-kernel.h
 /*-user.h
 /cfsin
diff --git a/tools/emul/Makefile b/tools/emul/Makefile
index 52804eb..d3ba997 100644
--- a/tools/emul/Makefile
+++ b/tools/emul/Makefile
@@ -1,6 +1,7 @@
 TARGETS = shell zasm
 KERNEL_HEADERS = shell-kernel.h zasm-kernel.h
 USER_HEADERS = zasm-user.h
+CFSPACK = ../cfspack/cfspack
 
 .PHONY: all
 all: $(TARGETS)
@@ -13,8 +14,14 @@ $(KERNEL_HEADERS):
 zasm-user.h: zasm_user.asm
 	scas -o - -I ../../apps/zasm $< | ./bin2c.sh USERSPACE | tee $@ > /dev/null
 
-shell: shell.c libz80/libz80.o shell-kernel.h ../cfspack/cfspack
-zasm: zasm.c libz80/libz80.o zasm-kernel.h zasm-user.h
+zasm-includes.h: ../../parts/z80 $(CFSPACK)
+	cp -rf $< zasm-includes
+	rm zasm-includes/README.md
+	$(CFSPACK) zasm-includes | ./bin2c.sh FSDEV | tee $@ > /dev/null
+	rm -rf zasm-includes
+
+shell: shell.c libz80/libz80.o shell-kernel.h $(CFSPACK)
+zasm: zasm.c libz80/libz80.o zasm-kernel.h zasm-user.h zasm-includes.h
 $(TARGETS):
 	cc $< libz80/libz80.o -o $@
 
@@ -22,7 +29,7 @@ libz80/libz80.o: libz80/z80.c
 	make -C libz80/codegen opcodes
 	gcc -Wall -ansi -g -c -o libz80/libz80.o libz80/z80.c
 
-../cfspack/cfspack:
+$(CFSPACK):
 	make -C ../cfspack
 
 .PHONY: clean
diff --git a/tools/emul/zasm.c b/tools/emul/zasm.c
index a74d2fa..b651e2f 100644
--- a/tools/emul/zasm.c
+++ b/tools/emul/zasm.c
@@ -3,6 +3,7 @@
 #include "libz80/z80.h"
 #include "zasm-kernel.h"
 #include "zasm-user.h"
+#include "zasm-includes.h"
 
 /* zasm reads from a specified blkdev, assemble the file and writes the result
  * in another specified blkdev. In our emulator layer, we use stdin and stdout
@@ -27,7 +28,9 @@
 // in sync with zasm_glue.asm
 #define USER_CODE 0x4800
 #define STDIO_PORT 0x00
-#define STDIN_SEEK 0x01
+#define STDIN_SEEK_PORT 0x01
+#define FS_DATA_PORT 0x02
+#define FS_SEEK_PORT 0x03
 
 // Other consts
 #define STDIN_BUFSIZE 0x8000
@@ -43,6 +46,11 @@ static int inpt_size;
 static int inpt_ptr;
 static uint8_t middle_of_seek_tell = 0;
 
+static uint8_t fsdev[0xffff] = {0};
+static uint16_t fsdev_size = 0;
+static uint16_t fsdev_ptr = 0;
+static uint8_t fsdev_middle_of_seek_tell = 0;
+
 static uint8_t io_read(int unused, uint16_t addr)
 {
     addr &= 0xff;
@@ -52,7 +60,7 @@ static uint8_t io_read(int unused, uint16_t addr)
         } else {
             return 0;
         }
-    } else if (addr == STDIN_SEEK) {
+    } else if (addr == STDIN_SEEK_PORT) {
         if (middle_of_seek_tell) {
             middle_of_seek_tell = 0;
             return inpt_ptr & 0xff;
@@ -63,6 +71,23 @@ static uint8_t io_read(int unused, uint16_t addr)
             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_middle_of_seek_tell) {
+            fsdev_middle_of_seek_tell = 0;
+            return fsdev_ptr & 0xff;
+        } else {
+#ifdef DEBUG
+            fprintf(stderr, "tell %d\n", fsdev_ptr);
+#endif
+            fsdev_middle_of_seek_tell = 1;
+            return fsdev_ptr >> 8;
+        }
     } else {
         fprintf(stderr, "Out of bounds I/O read: %d\n", addr);
         return 0;
@@ -77,7 +102,7 @@ static void io_write(int unused, uint16_t addr, uint8_t val)
 #ifndef MEMDUMP
         putchar(val);
 #endif
-    } else if (addr == STDIN_SEEK) {
+    } else if (addr == STDIN_SEEK_PORT) {
         if (middle_of_seek_tell) {
             inpt_ptr |= val;
             middle_of_seek_tell = 0;
@@ -88,6 +113,21 @@ static void io_write(int unused, uint16_t addr, uint8_t val)
             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_middle_of_seek_tell) {
+            fsdev_ptr |= val;
+            fsdev_middle_of_seek_tell = 0;
+#ifdef DEBUG
+            fprintf(stderr, "seek %d\n", fsdev_ptr);
+#endif
+        } else {
+            fsdev_ptr = (val << 8) & 0xff00;
+            fsdev_middle_of_seek_tell = 1;
+        }
     } else {
         fprintf(stderr, "Out of bounds I/O write: %d / %d\n", addr, val);
     }
@@ -112,6 +152,9 @@ int main()
     for (int i=0; i<sizeof(USERSPACE); i++) {
         mem[i+USER_CODE] = USERSPACE[i];
     }
+    for (int i=0; i<sizeof(FSDEV); i++) {
+        fsdev[i] = FSDEV[i];
+    }
     // read stdin in buffer
     inpt_size = 0;
     inpt_ptr = 0;