Update makefile, and bug fix in pio driver and usart

19 files changed, 532 insertions, 34 deletions

diff --git a/sw/z80/arch/addresses.h b/sw/z80/arch/include/addresses.h
index 07ab473..07ab473 100644
--- a/sw/z80/arch/addresses.h
+++ b/sw/z80/arch/include/addresses.h
diff --git a/sw/z80/arch/include/sleep.h b/sw/z80/arch/include/sleep.h
new file mode 100644
index 0000000..bd4214b
--- /dev/null
+++ b/sw/z80/arch/include/sleep.h
@@ -0,0 +1,14 @@
+#ifndef __SLEEP_H__
+#define __SLEEP_H__
+
+#ifndef F_CPU
+#error undefined CPU clock speed
+#endif
+
+#define SLEEP_UNIT ((F_CPU/4)/2)
+
+#include <stdint.h>
+
+void usleep(uint16_t microseconds);
+
+#endif // __SLEEP_H__
\ No newline at end of file
diff --git a/sw/z80/arch/makefile b/sw/z80/arch/makefile
new file mode 100644
index 0000000..2763c10
--- /dev/null
+++ b/sw/z80/arch/makefile
@@ -0,0 +1,27 @@
+# Drivers library
+
+LIB     := build/arch.a
+SOURCES := $(wildcard *.c)
+OBJECTS := $(patsubst %.c,build/%.rel,$(SOURCES))
+
+F_CPU := 10000
+
+CC := sdcc
+AR := sdar
+CFLAGS := -mz80 \
+			-Iinclude \
+			-DDEBUG \
+			-DF_CPU=$(F_CPU)
+
+.PHONY: dirs clean
+$(LIB): $(OBJECTS)
+	$(AR) rcs $@ $(OBJECTS)
+
+$(OBJECTS): build/%.rel: %.c $(SOURCES) dirs
+	$(CC) $(CFLAGS) -c $< -o $@
+
+dirs:
+	mkdir -p build
+
+clean:
+	- rm -rd build
diff --git a/sw/z80/arch/sleep.c b/sw/z80/arch/sleep.c
new file mode 100644
index 0000000..154e7ec
--- /dev/null
+++ b/sw/z80/arch/sleep.c
@@ -0,0 +1,16 @@
+#include "sleep.h"
+
+void usleep(uint16_t microseconds)
+{
+    __asm
+    pop hl
+loop:
+    ld bc, #SLEEP_UNIT
+unit:
+    nop
+    dec bc
+    jr nz, unit
+    dec hl
+    jr nz,loop
+    __endasm;
+}
\ No newline at end of file
diff --git a/sw/z80/drivers/include/pio.h b/sw/z80/drivers/include/pio.h
index a4b6fc2..a1137e4 100644
--- a/sw/z80/drivers/include/pio.h
+++ b/sw/z80/drivers/include/pio.h
@@ -10,23 +10,24 @@
 
 // registers
 #define PIO_REG_DATA 0
-#define PIO_REG_CTRL 1
+#define PIO_REG_CTRL 2
 
 // #define PIO_REG_DATA_A      (PIO_A + PIO_REG_PORT)
 // #define PIO_REG_DATA_B 1    (PIO_B + PIO_REG_PORT)
 // #define PIO_REG_CTRL_A 2    (PIO_A + PIO_REG_CTRL)
 // #define PIO_REG_CTRL_B 3    (PIO_B + PIO_REG_CTRL)
 
-#define PIO_MODE_BYTE_IN   0
-#define PIO_MODE_BYTE_OUT  1
-#define PIO_MODE_BYTE_BI   2
-#define PIO_MODE_BIT_IO    3
+#define PIO_MODE_BYTE_OUT  0 // mode 0
+#define PIO_MODE_BYTE_IN   1 // mode 1
+#define PIO_MODE_BYTE_BI   2 // mode 2
+#define PIO_MODE_BIT_IO    3 // mode 3
 
-#define PIO_INT_ACTIVE_HIGH     (1<<5)
-#define PIO_INT_AND_MODE        (1<<6)
-#define PIO_INT_ENABLE          (1<<7)
+#define PIO_INT_DISABLE         0 
+#define PIO_INT_ACTIVE_HIGH     2 
+#define PIO_INT_AND_MODE        4
+#define PIO_INT_ENABLE          8
 
-/* functions used internallyto interface with the device */
+/* functions used internally to interface with the device */
 inline void _pio_write(uint8_t reg, uint8_t data);
 inline uint8_t _pio_read(uint8_t reg);
 
diff --git a/sw/z80/drivers/include/usart.h b/sw/z80/drivers/include/usart.h
index bb06aab..fdc01e2 100644
--- a/sw/z80/drivers/include/usart.h
+++ b/sw/z80/drivers/include/usart.h
@@ -48,8 +48,8 @@
 #define USART_AUTOFLOW_CTS      2
 #define USART_AUTOFLOW_OFF      0
 
-typedef unsigned int    uint;
-typedef uint8_t         register_t;
+typedef unsigned int        uint;
+typedef volatile uint8_t    register_t;
 
 /* stuctures for usart registers */
 struct IER 
diff --git a/sw/z80/drivers/makefile b/sw/z80/drivers/makefile
index 98f453a..65ded58 100644
--- a/sw/z80/drivers/makefile
+++ b/sw/z80/drivers/makefile
@@ -6,15 +6,17 @@ OBJECTS := $(patsubst %.c,build/%.rel,$(SOURCES))
 
 CC := sdcc
 AR := sdar
-CFLAGS := -mz80 -Iinclude -I../arch -DDEBUG
+CFLAGS := -mz80 -Iinclude -I../arch/include -DDEBUG
 
-.PHONY: dirs clean
+.PHONY: dirs rebuild clean
 $(LIB): $(OBJECTS)
-	$(AR) rcs $@ $(OBJECTS)
+	$(AR) vrcs $@ $(OBJECTS)
 
 $(OBJECTS): build/%.rel: %.c $(SOURCES) dirs
 	$(CC) $(CFLAGS) -c $< -o $@
 
+rebuild: clean $(LIB)
+
 dirs:
 	mkdir -p build
 
diff --git a/sw/z80/drivers/pio.c b/sw/z80/drivers/pio.c
index 18697d8..272e191 100644
--- a/sw/z80/drivers/pio.c
+++ b/sw/z80/drivers/pio.c
@@ -1,6 +1,7 @@
 #include "pio.h"
 
-#if 0 /* old inline asm implementation */
+#ifdef PIO_ASM_INTERFACE
+/* old inline asm implementation */
 inline void _pio_write(uint8_t reg, uint8_t data)
 {
     __asm
@@ -17,7 +18,6 @@ inline void _pio_write(uint8_t reg, uint8_t data)
     __endasm;
 }
 
-// incomplete
 inline uint8_t _pio_read(uint8_t reg) __naked
 {
     __asm
@@ -31,7 +31,8 @@ inline uint8_t _pio_read(uint8_t reg) __naked
     ret
     __endasm;
 }
-#endif 
+
+#else
 
 inline void _pio_write(uint8_t reg, uint8_t data)
 {
@@ -43,6 +44,8 @@ inline uint8_t _pio_read(uint8_t reg)
     return *((uint8_t *) (ADDR_DEV_PIO + reg));
 }
 
+#endif
+
 void pio_set_mode(int port, int mode, uint8_t io)
 {
     // 0x0F is a control sequence to set mode
@@ -58,7 +61,7 @@ void pio_set_mode(int port, int mode, uint8_t io)
 void pio_set_interrupts(int port, int control)
 {
     // 0x07 is a control sequence to set interrupts
-    _pio_write((PIO_REG_CTRL + port), (control | 0x07));
+    _pio_write((PIO_REG_CTRL + port), (control<<4 | 0x07));
 }
 
 void pio_set_interrupts_mask(int port, int control, uint8_t mask)
diff --git a/sw/z80/drivers/usart.c b/sw/z80/drivers/usart.c
index 9ec6dbd..9a5ee38 100644
--- a/sw/z80/drivers/usart.c
+++ b/sw/z80/drivers/usart.c
@@ -1,6 +1,6 @@
 #include "usart.h"
 
-static struct _usart_device *_usart = (struct _usart_device *) ADDR_DEV_USART;
+static volatile struct _usart_device *_usart = ((struct _usart_device *) ADDR_DEV_USART);
 
 void usart_set_baudrate(uint16_t baudrate)
 {
diff --git a/sw/z80/tests/asm/main.s b/sw/z80/tests/asm/main.s
new file mode 100644
index 0000000..8cf4df0
--- /dev/null
+++ b/sw/z80/tests/asm/main.s
@@ -0,0 +1,40 @@
+    .module crt0
+    .area   _HEADER (ABS)
+
+;; Reset vectors
+    .org    0
+    jp  init
+
+    .org    0x38 ; the instruction 0xff (not written) resets to this location
+    jp init
+
+;; main code
+    .org    0x100
+    .globl  _main
+
+init:
+    ;; Set stack pointer directly above top of memory.
+    ld  sp,#0xffff
+
+    ;; Start of the program
+    call    _main
+    jp      _exit
+
+_exit:
+    halt
+    ; jp  _exit
+
+;; Ordering of segments for the linker.
+    .area   _HOME
+    .area   _CODE
+_main:
+    ret
+    .area   _INITIALIZER
+    .area   _GSINIT
+    .area   _GSFINAL
+
+    .area   _DATA
+    .area   _INITIALIZED
+    .area   _BSEG
+    .area   _BSS
+    .area   _HEAP
diff --git a/sw/z80/tests/asm/makefile b/sw/z80/tests/asm/makefile
new file mode 100644
index 0000000..413b0fe
--- /dev/null
+++ b/sw/z80/tests/asm/makefile
@@ -0,0 +1,47 @@
+####
+# source code settings
+#
+OSNAME := ram_test
+ 
+CSOURCES 	:=  $(wildcard *.s)
+
+OBJECTS 	:= $(patsubst %.s,build/%.rel,$(SOURCES))
+HEXFILE		:= build/$(OSNAME).hex
+BINARY  	:= build/$(OSNAME).bin
+
+### 
+# compiler settings
+#
+ASM		:= sdasz80
+LD		:= sdldz80
+
+FLAGS	:= 
+LDFLAGS :=
+
+.PHONY: flash dirs dis clean
+all: $(BINARY)
+
+flash: $(BINARY)
+	minipro -p M28C64 -w $< 
+
+# build binary
+$(BINARY): $(OBJECTS) dirs
+	$(LD) $(LDFLAGS) $(OBJECTS) -o $(HEXFILE)
+	makebin -s 8192 -yo 1 $(HEXFILE) $(BINARY)
+
+$(OBJECTS): build/%.rel : %.s $(SOURCES) dirs
+	@printf "\n"
+	$(ASM) $(FLAGS) $< -o
+
+build/crt0.rel: crt0.s
+	sdasz80 -o $<
+	@mv crt0.rel build/
+
+dirs:
+	mkdir -p build
+
+dis: $(BINARY)
+	r2 -a z80 $< -c 'pd 0x10; s 0x100; pd 10; s 0x200; pd 10'
+
+clean:
+	- rm -rd build
diff --git a/sw/z80/tests/pio/crt0.s b/sw/z80/tests/pio/crt0.s
index eabe06c..c900065 100644
--- a/sw/z80/tests/pio/crt0.s
+++ b/sw/z80/tests/pio/crt0.s
@@ -36,5 +36,3 @@ _exit:
     .area   _BSEG
     .area   _BSS
     .area   _HEAP
-
-    .area   _CODE
\ No newline at end of file
diff --git a/sw/z80/tests/pio/dis.txt b/sw/z80/tests/pio/dis.txt
new file mode 100644
index 0000000..60bef8e
--- /dev/null
+++ b/sw/z80/tests/pio/dis.txt
@@ -0,0 +1,225 @@
+mkdir -p build
+
+sdcc -mz80 --allow-unsafe-read -I . -I ../../arch/include -I ../../drivers/include -DDEBUG -c main.c -o build/main.rel
+sdcc -mz80 --no-std-crt0 build/crt0.rel -L ../../drivers/build -l drivers.a -pedantic  build/main.rel -o build/pio_test.hex
+makebin -s 8192 -yo 1 build/pio_test.hex build/pio_test.bin
+#dz80 -b -n build/pio_test.bin
+r2 -a z80 build/pio_test.bin -A \
+-c 'afr main 0x200; \
+	pd 0x10; \
+	s 0x100; \
+	pd 10; \
+	s 0x200; \
+	pd 0xa0' \
+
+/ (fcn) fcn.00000000 13
+|   fcn.00000000 ();
+|              ; XREFS: DATA 0x00000202  DATA 0x00000204  DATA 0x00000209  DATA 0x0000020c  DATA 0x00000216  DATA 0x00000219  DATA 0x00000220  DATA 0x00000221  
+|              ; XREFS: DATA 0x00000226  DATA 0x00000256  
+\       ,=< 0x00000000      c30001         jp loc.00000100
+        |   0x00000003      ff             rst 0x38
+        |   0x00000004      ff             rst 0x38
+        |   0x00000005      ff             rst 0x38
+        |   0x00000006      ff             rst 0x38
+        |   0x00000007      ff             rst 0x38
+        |   0x00000008      ff             rst 0x38
+        |   0x00000009      ff             rst 0x38
+        |   0x0000000a      ff             rst 0x38
+        |   0x0000000b      ff             rst 0x38
+        |   0x0000000c      ff             rst 0x38
+        |   0x0000000d      ff             rst 0x38
+        |   0x0000000e      ff             rst 0x38
+        |   0x0000000f      ff             rst 0x38
+        |   0x00000010      ff             rst 0x38
+        |   0x00000011      ff             rst 0x38
+|- loc.00000100 10
+|   loc.00000100 ();
+|              ; JMP XREF from 0x00000000 (fcn.00000000)
+|              ; JMP XREF from 0x00000106 (loc.00000100)
+|           0x00000100      31ffff         ld sp, 0xffff
+|           0x00000103      cd0002         call main
+|       ,=< 0x00000106      c30901         jp 0x0109
+|       |      ; JMP XREF from 0x00000106 (loc.00000100)
+\       `-> 0x00000109      76             halt
+            0x0000010a      ff             rst 0x38
+            0x0000010b      ff             rst 0x38
+            0x0000010c      ff             rst 0x38
+            0x0000010d      ff             rst 0x38
+            0x0000010e      ff             rst 0x38
+            0x0000010f      ff             rst 0x38
+/ (fcn) main 50
+|   main ();
+|              ; CALL XREF from 0x00000103 (loc.00000100)
+|              ; CALL XREF from 0x00000200 (main)
+|           0x00000200      0600           ld b, 0x00
+|           0x00000202      c5             push bc
+|           0x00000203      af             xor a
+|           0x00000204      f5             push af
+|           0x00000205      33             inc sp
+|           0x00000206      210300         ld hl, 0x0003
+|           0x00000209      e5             push hl
+|           0x0000020a      2e00           ld l, 0x00
+|           0x0000020c      e5             push hl
+|           0x0000020d      cd5502         call fcn.00000255
+|           0x00000210      f1             pop af
+|           0x00000211      f1             pop af
+|           0x00000212      33             inc sp
+|           0x00000213      210000         ld hl, 0x0000
+|           0x00000216      e5             push hl
+|           0x00000217      2e00           ld l, 0x00
+|           0x00000219      e5             push hl
+|           0x0000021a      cd8e02         call fcn.0000028e
+|           0x0000021d      f1             pop af
+|           0x0000021e      f1             pop af
+\           0x0000021f      c1             pop bc
+|              ; JMP XREF from 0x00000230 (main)
+|       .-> 0x00000220      c5             push bc
+|       |   0x00000221      c5             push bc
+|       |   0x00000222      33             inc sp
+|       |   0x00000223      210000         ld hl, 0x0000
+|       |   0x00000226      e5             push hl
+|       |   0x00000227      cde002         call fcn.000002e0
+|       |   0x0000022a      f1             pop af
+|       |   0x0000022b      33             inc sp
+|       |   0x0000022c      c1             pop bc
+|       |   0x0000022d      78             ld a, b
+|       |   0x0000022e      2f             cpl
+|       |   0x0000022f      47             ld b, a
+|       `=< 0x00000230      18ee           jr 0xee
+            0x00000232      210200         ld hl, 0x0002
+            0x00000235      39             add hl, sp
+            0x00000236      4e             ld c, [hl]
+            0x00000237      0600           ld b, 0x00
+            0x00000239      210042         ld hl, 0x4200
+            0x0000023c      09             add hl, bc
+            0x0000023d      fd210300       ld iy, 0x0003
+            0x00000241      fd39           add iy, sp
+            0x00000243      fd7e00         ld a, [iy+0x00]
+            0x00000246      77             ld [hl], a
+            0x00000247      c9             ret
+            0x00000248      210200         ld hl, 0x0002
+            0x0000024b      39             add hl, sp
+            0x0000024c      4e             ld c, [hl]
+            0x0000024d      0600           ld b, 0x00
+            0x0000024f      210042         ld hl, 0x4200
+            0x00000252      09             add hl, bc
+            0x00000253      6e             ld l, [hl]
+            0x00000254      c9             ret
+/ (fcn) fcn.00000255 8
+|   fcn.00000255 ();
+|              ; CALL XREF from 0x0000020d (main)
+|           0x00000255      dde5           push ix
+|           0x00000257      dd210000       ld ix, 0x0000
+\           0x0000025b      dd39           add ix, sp
+            0x0000025d      dd7e06         ld a, [ix+0x06]
+            0x00000260      0f             rrca
+            0x00000261      0f             rrca
+            0x00000262      e6c0           and 0xc0
+            0x00000264      f60f           or 0x0f
+            0x00000266      57             ld d, a
+            0x00000267      dd5e04         ld e, [ix+0x04]
+            0x0000026a      1c             inc e
+            0x0000026b      1c             inc e
+            0x0000026c      6b             ld l, e
+            0x0000026d      2600           ld h, 0x00
+            0x0000026f      010042         ld bc, 0x4200
+            0x00000272      09             add hl, bc
+            0x00000273      72             ld [hl], d
+            0x00000274      dd7e06         ld a, [ix+0x06]
+            0x00000277      d603           sub 0x03
+        ,=< 0x00000279      2010           jr nz, 0x10
+        |   0x0000027b      dd7e07         ld a, [ix+0x07]
+        |   0x0000027e      b7             or a
+       ,==< 0x0000027f      200a           jr nz, 0x0a
+       ||   0x00000281      dd4e08         ld c, [ix+0x08]
+       ||   0x00000284      1600           ld d, 0x00
+       ||   0x00000286      210042         ld hl, 0x4200
+       ||   0x00000289      19             add hl, de
+       ||   0x0000028a      71             ld [hl], c
+       ``-> 0x0000028b      dde1           pop ix
+            0x0000028d      c9             ret
+/ (fcn) fcn.0000028e 29
+|   fcn.0000028e ();
+|              ; CALL XREF from 0x0000021a (main)
+|           0x0000028e      210400         ld hl, 0x0004
+|           0x00000291      39             add hl, sp
+|           0x00000292      7e             ld a, [hl]
+|           0x00000293      07             rlca
+|           0x00000294      07             rlca
+|           0x00000295      07             rlca
+|           0x00000296      07             rlca
+|           0x00000297      e6f0           and 0xf0
+|           0x00000299      f607           or 0x07
+|           0x0000029b      4f             ld c, a
+|           0x0000029c      210200         ld hl, 0x0002
+|           0x0000029f      39             add hl, sp
+|           0x000002a0      5e             ld e, [hl]
+|           0x000002a1      1c             inc e
+|           0x000002a2      1c             inc e
+|           0x000002a3      1600           ld d, 0x00
+|           0x000002a5      210042         ld hl, 0x4200
+|           0x000002a8      19             add hl, de
+|           0x000002a9      71             ld [hl], c
+\           0x000002aa      c9             ret
+            0x000002ab      dde5           push ix
+            0x000002ad      dd210000       ld ix, 0x0000
+            0x000002b1      dd39           add ix, sp
+            0x000002b3      dd7e06         ld a, [ix+0x06]
+            0x000002b6      f617           or 0x17
+            0x000002b8      57             ld d, a
+            0x000002b9      dd5e04         ld e, [ix+0x04]
+            0x000002bc      1c             inc e
+            0x000002bd      1c             inc e
+            0x000002be      6b             ld l, e
+            0x000002bf      2600           ld h, 0x00
+            0x000002c1      010042         ld bc, 0x4200
+            0x000002c4      09             add hl, bc
+            0x000002c5      72             ld [hl], d
+            0x000002c6      dd4e08         ld c, [ix+0x08]
+            0x000002c9      1600           ld d, 0x00
+            0x000002cb      210042         ld hl, 0x4200
+            0x000002ce      19             add hl, de
+            0x000002cf      71             ld [hl], c
+            0x000002d0      dde1           pop ix
+            0x000002d2      c9             ret
+            0x000002d3      210200         ld hl, 0x0002
+            0x000002d6      39             add hl, sp
+            0x000002d7      4e             ld c, [hl]
+            0x000002d8      0600           ld b, 0x00
+            0x000002da      210042         ld hl, 0x4200
+            0x000002dd      09             add hl, bc
+            0x000002de      6e             ld l, [hl]
+            0x000002df      c9             ret
+/ (fcn) fcn.000002e0 18
+|   fcn.000002e0 ();
+|              ; CALL XREF from 0x00000227 (main)
+|           0x000002e0      210400         ld hl, 0x0004
+|           0x000002e3      39             add hl, sp
+|           0x000002e4      4e             ld c, [hl]
+|           0x000002e5      210200         ld hl, 0x0002
+|           0x000002e8      39             add hl, sp
+|           0x000002e9      5e             ld e, [hl]
+|           0x000002ea      1600           ld d, 0x00
+|           0x000002ec      210042         ld hl, 0x4200
+|           0x000002ef      19             add hl, de
+|           0x000002f0      71             ld [hl], c
+\           0x000002f1      c9             ret
+            0x000002f2      ff             rst 0x38
+            0x000002f3      ff             rst 0x38
+            0x000002f4      ff             rst 0x38
+            0x000002f5      ff             rst 0x38
+            0x000002f6      ff             rst 0x38
+            0x000002f7      ff             rst 0x38
+            0x000002f8      ff             rst 0x38
+            0x000002f9      ff             rst 0x38
+            0x000002fa      ff             rst 0x38
+            0x000002fb      ff             rst 0x38
+            0x000002fc      ff             rst 0x38
+            0x000002fd      ff             rst 0x38
+            0x000002fe      ff             rst 0x38
+            0x000002ff      ff             rst 0x38
+            0x00000300      ff             rst 0x38
+            0x00000301      ff             rst 0x38
+            0x00000302      ff             rst 0x38
+ -- Change the graph block definition with graph.callblocks, graph.jmpblocks, graph.flagblocks
+

[0x00000200]> 



[0x00000200]> q
[0x00000200]> q



[0x00000200]> q
diff --git a/sw/z80/tests/pio/main.c b/sw/z80/tests/pio/main.c
index c1f3741..c873e20 100644
--- a/sw/z80/tests/pio/main.c
+++ b/sw/z80/tests/pio/main.c
@@ -6,12 +6,11 @@ void main(void)
 {
     uint8_t i = 0;
 
-    pio_set_mode(PIO_A, PIO_MODE_BYTE_OUT, 0);
+    pio_set_mode(PIO_A, PIO_MODE_BIT_IO, 0x00);
+    pio_set_interrupts(PIO_A, PIO_INT_DISABLE);
 
     while (1) {
         pio_write(PIO_A, i);
         i = ~i;
     }
-
-    // return;
 }
diff --git a/sw/z80/tests/pio/makefile b/sw/z80/tests/pio/makefile
index 5c3716c..f7f97be 100644
--- a/sw/z80/tests/pio/makefile
+++ b/sw/z80/tests/pio/makefile
@@ -4,6 +4,8 @@
 OSNAME := pio_test
  
 CSOURCES 	:=  $(wildcard *.c)
+LIBS 		:= ../../arch/build/arch.a \
+			   ../../drivers/build/drivers.a
 
 OBJECTS 	:= $(patsubst %.c,build/%.rel,$(CSOURCES))
 HEXFILE		:= build/$(OSNAME).hex
@@ -15,9 +17,10 @@ BINARY  	:= build/$(OSNAME).bin
 CC 		:= sdcc
 
 CFLAGS	:= -mz80 \
+			--no-std-crt0 build/crt0.rel \
 			--allow-unsafe-read \
 			-I . \
-			-I ../../arch \
+			-I ../../arch/include \
 			-I ../../drivers/include \
 			-DDEBUG
 
@@ -25,9 +28,8 @@ LDFLAGS := -mz80 \
 			--no-std-crt0 build/crt0.rel \
 			-L ../../drivers/build \
 			-l drivers.a \
-			-pedantic 
-
-			# --code-loc 0x0120 \
+			-pedantic \
+			--code-loc 0x0200
 			# --data-loc 0x2000
 
 .PHONY: flash dirs dis clean
@@ -41,10 +43,14 @@ $(BINARY): $(OBJECTS) dirs
 	$(CC) $(LDFLAGS) $(OBJECTS) -o $(HEXFILE)
 	makebin -s 8192 -yo 1 $(HEXFILE) $(BINARY)
 
-$(OBJECTS): build/%.rel : %.c $(CSOURCES) dirs build/crt0.rel
+$(OBJECTS): build/%.rel : %.c $(CSOURCES) dirs build/crt0.rel $(LIBS)
 	@printf "\n"
 	$(CC) $(CFLAGS) -c $< -o $@
 
+$(LIBS): %.a:
+	@printf "\n"
+	make -C $(shell printf $@ | sed 's:build.*.::')
+
 build/crt0.rel: crt0.s
 	sdasz80 -o $<
 	@mv crt0.rel build/
@@ -53,14 +59,14 @@ dirs:
 	mkdir -p build
 
 dis: $(BINARY)
-	#dz80 -b -n $<
-	r2 -a z80 $< -A \
-	-c 'afr main 0x200; \
+	dz80 -b -n -t $(BINARY)
+	r2 -a z80 $< \
+	-c 'afn main 0x200; \
 		pd 0x10; \
 		s 0x100; \
 		pd 10; \
 		s 0x200; \
-		pd 0x40' \
+		pd 0x95'
 
 clean:
 	- rm -rd build
diff --git a/sw/z80/tests/ram/makefile b/sw/z80/tests/ram/makefile
index 3db0a67..f8eb9fc 100644
--- a/sw/z80/tests/ram/makefile
+++ b/sw/z80/tests/ram/makefile
@@ -48,7 +48,6 @@ dirs:
 	mkdir -p build
 
 dis: $(BINARY)
-	#dz80 -b -n $<
 	r2 -a z80 $< -c 'pd 0x10; s 0x100; pd 10; s 0x200; pd 10'
 
 clean:
diff --git a/sw/z80/tests/usart/crt0.s b/sw/z80/tests/usart/crt0.s
new file mode 100644
index 0000000..c900065
--- /dev/null
+++ b/sw/z80/tests/usart/crt0.s
@@ -0,0 +1,38 @@
+    .module crt0
+    .area   _HEADER (ABS)
+
+;; Reset vectors
+    .org    0
+    jp  init
+
+    .org    0x38 ; the instruction 0xff (not written) resets to this location
+    jp init
+
+;; main code
+    .org    0x100
+    .globl  _main
+
+init:
+    ;; Set stack pointer directly above top of memory.
+    ld  sp,#0xffff
+
+    ;; Start of the program
+    call    _main
+    jp      _exit
+
+_exit:
+    halt
+    ; jp  _exit
+
+;; Ordering of segments for the linker.
+    .area   _HOME
+    .area   _CODE
+    .area   _INITIALIZER
+    .area   _GSINIT
+    .area   _GSFINAL
+
+    .area   _DATA
+    .area   _INITIALIZED
+    .area   _BSEG
+    .area   _BSS
+    .area   _HEAP
diff --git a/sw/z80/tests/usart/main.c b/sw/z80/tests/usart/main.c
new file mode 100644
index 0000000..a905df2
--- /dev/null
+++ b/sw/z80/tests/usart/main.c
@@ -0,0 +1,11 @@
+#include "usart.h"
+#include <stdint.h>
+
+void main(void)
+{
+    usart_init(USART_BAUDRATE_1200, USART_PARITY_NONE, USART_STOP_BITS_1);
+
+    while (1) {
+        usart_write("Hello World!\n", 13);
+    }
+}
diff --git a/sw/z80/tests/usart/makefile b/sw/z80/tests/usart/makefile
new file mode 100644
index 0000000..8aaf6b1
--- /dev/null
+++ b/sw/z80/tests/usart/makefile
@@ -0,0 +1,72 @@
+####
+# source code settings
+#
+OSNAME := usart_test
+ 
+CSOURCES 	:=  $(wildcard *.c)
+LIBS 		:= ../../arch/build/arch.a \
+			   ../../drivers/build/drivers.a
+
+OBJECTS 	:= $(patsubst %.c,build/%.rel,$(CSOURCES))
+HEXFILE		:= build/$(OSNAME).hex
+BINARY  	:= build/$(OSNAME).bin
+
+### 
+# compiler settings
+#
+CC 		:= sdcc
+
+CFLAGS	:= -mz80 \
+			--no-std-crt0 build/crt0.rel \
+			--allow-unsafe-read \
+			-I . \
+			-I ../../arch/include \
+			-I ../../drivers/include \
+			-DDEBUG
+
+LDFLAGS := -mz80 \
+			--no-std-crt0 build/crt0.rel \
+			-L ../../drivers/build \
+			-l drivers.a \
+			-pedantic \
+			--code-loc 0x0200
+			# --data-loc 0x2000
+
+.PHONY: flash dirs dis clean
+all: $(BINARY)
+
+flash: $(BINARY)
+	minipro -p M28C64 -w $< 
+
+# build binary
+$(BINARY): $(OBJECTS) dirs
+	$(CC) $(LDFLAGS) $(OBJECTS) -o $(HEXFILE)
+	makebin -s 8192 -yo 1 $(HEXFILE) $(BINARY)
+
+$(OBJECTS): build/%.rel : %.c $(CSOURCES) dirs build/crt0.rel $(LIBS)
+	@printf "\n"
+	$(CC) $(CFLAGS) -c $< -o $@
+
+$(LIBS): %.a:
+	@printf "\n"
+	make -C $(shell printf $@ | sed 's:build.*.::')
+
+build/crt0.rel: crt0.s
+	sdasz80 -o $<
+	@mv crt0.rel build/
+
+dirs:
+	mkdir -p build
+
+dis: $(BINARY)
+	dz80 -b -n -t $(BINARY)
+	r2 -a z80 $< \
+	-c 'afn main 0x200; \
+		pd 0x10; \
+		s 0x100; \
+		pd 10; \
+		s 0x200; \
+		pd 0x95'
+
+clean:
+	- rm -rd build