Overhaul the template.

- DATA and RODATA segments added to computer.cfg
 - RAM memory configuration now starts at  to not overwrite the cpu stack
 - hardware.inc added to handle hardware related constants
 - constants removed from via.s
 - constants removed from serial.s
 - serial_delay from serial.s is now dynamic, dependant on CPU_HZ and baud rate
 - serial_baud_* functions added to setup 19200 and 9600 baud
 - mem_copy.s added. data copy functions are to be implemented here
 - copy_data (mem_copy.s) implemented to copy the DATA segment from ROM to RAM
 - propper system setup in main.s
 - Makefile now generates a .map file with the memory map information

.gitignore

@@ -31,3 +31,6 @@ bin/
 
 
 .idea/
+symon*.jar
+*.bin
+*.map

Makefile

@@ -1,6 +1,8 @@
 OUTPUT := example.bin
 TARGET_CPU := 65c02
 
+MEM_MAP_FILE := $(OUTPUT:.bin=.map)
+
 # Tool list
 CC65 := cc65
 CA65 := ca65
@@ -20,7 +22,7 @@ all: $(OUTPUT)
 
 $(OUTPUT): $(C_SOURCES) $(ASM_SOURCES)
 	@mkdir -p $(dir $@)
-	$(CL65) -t none --cpu $(TARGET_CPU) -C computer.cfg -O -o $@ $^
+	$(CL65) -t none --cpu $(TARGET_CPU) -C computer.cfg -m $(MEM_MAP_FILE) -O -o $@ $^
 
 clean:
 	rm -f $(OBJECTS)

computer.cfg

@@ -1,7 +1,7 @@
 # Physical Memory configuration
 MEMORY {
     ZP:     start = $00,    size = $0100,   type = rw,  file = "";
-    RAM:    start = $0100,  size = $7e00,   type = rw,  file = "";
+    RAM:    start = $0200,  size = $7d00,   type = rw,  file = "";
     PRG:    start = $C000,  size = $4000,   type = ro,  file = %O,  fill = yes, fillval = $00;
 }
 
@@ -10,5 +10,7 @@ SEGMENTS {
     ZEROPAGE:   load = ZP,  type = zp;
     BSS:        load = RAM, type = bss;
     CODE:       load = PRG, type = ro, start = $C000;
+    DATA:       load = PRG, run = RAM, type = rw, define = yes;
+    RODATA:     load = PRG, type = ro;
     VECTORS:    load = PRG, type = ro, start = $FFFA;
 }

src/hardware/hardware.inc

@@ -0,0 +1,31 @@
+.ifndef HARDWARE_INC
+HARDWARE_INC = 1
+
+; CPU settings
+CPU_HZ = 1843200
+
+; Serial/ACIA addresses
+SERIAL_DATA = $8400
+SERIAL_STATUS = $8401
+SERIAL_COMMAND = $8402
+SERIAL_CONTROL = $8403
+
+; VIA addresses
+VIA_PORTB = $8000
+VIA_PORTA = $8001
+VIA_DDRB = $8002
+VIA_DDRA = $8003
+VIA_T1C_L = $8004
+VIA_T1C_H = $8005
+VIA_T1L_L = $8006
+VIA_T1L_H = $8007
+VIA_T2C_L = $8008
+VIA_T2C_H = $8009
+VIA_SR = $800a
+VIA_ACR = $800b
+VIA_PCR = $800c
+VIA_IFR = $800d
+VIA_IER = $800e
+VIA_PORTA_2 = $800f
+
+.endif

src/hardware/serial.s

@@ -1,14 +1,38 @@
 ; Serial port helper function
 ; Serial is handled by the 65c51n (this thing has a few bugs)
-.export serial_setup
+.export serial_setup, serial_recv_char, serial_print_char, serial_baud_19200, serial_baud_9600
-.export serial_recv_char
-.export serial_print_char
 
-SERIAL_DATA = $8400
+.include "hardware.inc"
-SERIAL_STATUS = $8401
-SERIAL_COMMAND = $8402
-SERIAL_CONTROL = $8403
 
+; -----------------------------
+; Active wait loop calculations
+; -----------------------------
+INNER_LOOP  = 9     ; Inner loop count (sets granularity of the waiting period)
+
+; cycles per outer pass: ldx(2) + innerLoop(5*INNER_LOOP-1) + dey(2) + bne(3)
+PASS_CYC    = INNER_LOOP * 5 + 6
+
+; passes for each 10bit frame (8N1), rounded up
+PASSES_19200 = (10 * CPU_HZ/19200 + PASS_CYC - 1) / PASS_CYC
+PASSES_9600  = (10 * CPU_HZ/9600  + PASS_CYC - 1) / PASS_CYC
+
+.assert PASSES_9600 < 256, error, "CPU clock too fast for this delay; raise INNER_LOOP"
+
+; ACIA control register presets: internal BAUD, 8N1
+SERIAL_CTRL_19200 = %00011111
+SERIAL_CTRL_9600  = %00011110
+                ;  ||||````- 19200/9600 baud
+                ;  |||`----- Receiver clock is baud rate
+                ;  |``------ 8bit word
+                ;  `-------- 1 stop bit
+
+; -----------------------------
+; -----------------------------
+
+.zeropage
+tx_passes: .res 1   ; Variable to store outer loop passes
+
+.code
 serial_setup:
     ; 65c51n has a few bugs. check http://forum.6502.org/viewtopic.php?f=4&t=2543&start=30#p29795
     lda #$00
@@ -21,19 +45,21 @@ serial_setup:
                         ;    |`------ Receiver normal mode
                         ;    `------- Parity disabled
 
-    lda #$1f            ; %0001 1111
+    jsr serial_baud_19200
-    sta SERIAL_CONTROL  ;  |||| ````- 19200 baud
-                        ;  |||`------ Receiver clock is baud rate
-                        ;  |``------- 8bit word
-                        ;  `--------- 1 stop bit
     rts
 
-serial_print_char:
+serial_baud_19200:
-    pha                 ; Save A to stack (character)
+    lda #SERIAL_CTRL_19200
-    lda SERIAL_STATUS   ; read status register and ignore the value
+    sta SERIAL_CONTROL
-    pla                 ; return character from stack
+    lda #PASSES_19200
-    sta SERIAL_DATA     ; send character
+    sta tx_passes
-    jsr serial_delay    ; comment out for older 6551/65c51
+    rts
+
+serial_baud_9600:
+    lda #SERIAL_CTRL_9600
+    sta SERIAL_CONTROL
+    lda #PASSES_9600
+    sta tx_passes
     rts
 
 serial_recv_char:
@@ -43,18 +69,22 @@ serial_recv_char:
     lda SERIAL_DATA     ; get byte
     rts
 
+serial_print_char:
+    sta SERIAL_DATA     ; send character
+    ;fall through to the delay routine
+
 serial_delay:
-    phy     ; save y reg
+    phy             ; save y reg
-    phx     ; save x register
+    phx             ; save x register
-    ldy #6  ; delay value (clock rate in mhz 2 clock cycles)
+    ldy tx_passes   ; outer passes
 @ydelay:
-    ldx #$68    ; Init x register
+    ldx #INNER_LOOP ; Init x register
-@xdelay:
+@xdelay:            ; loop time was calculated above by the assembler
-    dex         ; decrement low index
+    dex             ; decrement low index
-    bne @xdelay ; loop back until x is 0
+    bne @xdelay     ; loop back until x is 0
-    dey         ; decrement high
+    dey             ; decrement high
-    bne @ydelay ; loop until y is 0
+    bne @ydelay     ; loop until y is 0
 @delay_done:
-    plx         ; return x
+    plx             ; return x
-    ply         ; return y
+    ply             ; return y
     rts

src/hardware/via.s

@@ -1,18 +1 @@
-; Addresses for the VIA 65c22
+.include "hardware.inc"
-
-VIA_PORTB = $8000
-VIA_PORTA = $8001
-VIA_DDRB = $8002
-VIA_DDRA = $8003
-VIA_T1C_L = $8004
-VIA_T1C_H = $8005
-VIA_T1L_L = $8006
-VIA_T1L_H = $8007
-VIA_T2C_L = $8008
-VIA_T2C_H = $8009
-VIA_SR = $800a
-VIA_ACR = $800b
-VIA_PCR = $800c
-VIA_IFR = $800d
-VIA_IER = $800e
-VIA_PORTA_2 = $800f

src/main.s

@@ -1,40 +1,72 @@
-.import serial_setup
+.import serial_setup, serial_print_char, serial_recv_char
-.import serial_print_char
+.import copy_data
 
-.segment "ZEROPAGE"
+; ---------------
+;       ZP
+; ---------------
+.zeropage
 ; Zero-page variables ($0000 - $00ff)
 
-.segment "BSS"
+; ---------------
-; RAM variables ($0100 - $7fff)
+;       BSS
+; ---------------
+.bss
+; RAM variables ($0200 - $7fff)
 
-.segment "CODE"
+; ---------------
+;      DATA
+; ---------------
+.data
+; Initialized RAM variables ($0200 - $7fff)
+
+; ---------------
+;      CODE
+; ---------------
+.code
 ; Actual program code ($c000 - $fff9)
+reset:                              ; Program starts here
+; System setup
+    sei                             ; disable interrupts while setting things up
+    cld                             ; clear BCD mode flag (undefined on NMOS 6502, auto cleared on 65C02)
+    ldx #$ff
+    txs                             ; Reset stack pointer
 
-reset:  ; Program starts here
+    jsr copy_data                   ; copy data variables from ROM to RAM
-    jsr serial_setup
 
+    jsr serial_setup                ; setup serial interface (65C51N). 19200 baud set as default
+
+print_hello_world:
     ldx #0
-hello_world_loop:
+@loop:
-    lda str_hello_world,x   ; get char
+    lda str_hello_world,x           ; get char
-    beq hello_world_end     ; IF char is 0, done
+    beq @end                        ; IF char is 0, done
-    jsr serial_print_char   ; send char to console
+    jsr serial_print_char           ; send char to console
-    inx                     ; increment x (next char)
+    inx                             ; increment x (next char)
-    jmp hello_world_loop
+    jmp @loop
-hello_world_end:
+@end:
-    jmp hello_world_end
+    jmp @end
 
 
-irq:    ; IRQ Handler
+irq_handler:                        ; IRQ Handler
-    rti ; Do nothing
+    rti                             ; Do nothing
 
-nmi:    ; NMI handler
+nmi_handler:                        ; NMI handler
-    rti ; Do nothing
+    rti                             ; Do nothing
 
-str_hello_world:
-.asciiz "Hello, World!"
 
+; ---------------
+;     RODATA
+; ---------------
+.rodata
+; Constants
+str_hello_world: .asciiz "Hello, World!"
+
+
+; ---------------
+;     VECTORS
+; ---------------
 .segment "VECTORS"
 ; NMI, RESET and IRQ vectors
-.word nmi
+.word nmi_handler
 .word reset
-.word irq
+.word irq_handler

src/mem_copy.s

@@ -0,0 +1,46 @@
+.import __DATA_LOAD__, __DATA_RUN__, __DATA_SIZE__
+.export copy_data
+
+.zeropage
+src: .res 2
+dst: .res 2
+
+.code
+copy_data:
+; Copy data segment from ROM to final RAM location
+    lda #<__DATA_LOAD__     ; get source address low byte
+    sta src
+    lda #>__DATA_LOAD__     ; get source address high byte
+    sta src+1
+
+    lda #<__DATA_RUN__      ; get runtime final address low byte
+    sta dst
+    lda #>__DATA_RUN__      ; get runtime final address high byte
+    sta dst+1
+
+    ldx #>__DATA_SIZE__     ; number of 256 byte pages to copy (high byte)
+    beq @tail               ; if no full pages to copy, skip
+    ldy #0
+
+@page:
+    lda (src),y             ; grab byte
+    sta (dst),y             ; store byte
+    iny
+    bne @page               ; for 256 cycles
+    inc src+1               ; increment source high byte (next memory page)
+    inc dst+1               ; increment destination high byte (next memory page)
+    dex                     ; decrement full pages counter
+    bne @page               ; if no more full pages, stop
+
+@tail:                      ; copy remaining non full page
+    ldy #0
+    cpy #<__DATA_SIZE__     ; check if there is data to copy
+    beq @done               ; if no data, done
+@byte:
+    lda (src),y
+    sta (dst),y
+    iny
+    cpy #<__DATA_SIZE__     ; when y == __DATA_SIZE__, done
+    bne @byte               ; else, continue
+@done:
+    rts