Add ROM linked in read-only data section, at 6502's 0xc000-0xffff

src/Makefile

@@ -15,6 +15,8 @@ SRC =			\
 	cdcacm.c	\
 	main.c		\
 
+ROM = ../osi_bas/ROM.HEX
+
 CROSS_COMPILE ?= arm-none-eabi-
 CC = $(CROSS_COMPILE)gcc
 OBJCOPY = $(CROSS_COMPILE)objcopy
@@ -38,6 +40,7 @@ host_clean:
 	-$(Q)$(RM) pill_6502.bin
 
 OBJ = $(SRC:.c=.o)
+OBJ += $(ROM:.HEX=.o)
 
 pill_6502.elf: version.h $(OBJ)
 	@echo "  LD      $@"
@@ -47,6 +50,12 @@ pill_6502.elf: version.h $(OBJ)
 	@echo "  CC      $<"
 	$(Q)$(CC) $(CFLAGS) -c $< -o $@
 
+%.o:	%.HEX
+	@echo "  OBJCOPY $@.bin"
+	$(Q)$(OBJCOPY) -I ihex -O binary $^ $@.bin
+	@echo "  OBJCOPY $@"
+	$(Q)$(OBJCOPY) -I binary -O elf32-littlearm -B arm --rename-section .data=.rodata,alloc,load,readonly,data,contents $@.bin $@
+
 %.bin:	%.elf
 	@echo "  OBJCOPY $@"
 	$(Q)$(OBJCOPY) -O binary $^ $@

src/main.c

@@ -30,6 +30,7 @@
 #include <libopencm3/usb/cdc.h>
 
 #include "fake6502.h"
+#include "rom.h"
 #include "cdcacm.h"
 #include "version.h"
 
@@ -137,12 +138,19 @@ uint8_t usbd_control_buffer[128];
 
 // 6502 processor memory, 16KB (< 20KB)
 uint8_t ram[0x4000];
+// TODO: serial interface, 0xa000-0xbfff
 uint8_t read6502(uint16_t address) {
+	// RAM
 	if (address < sizeof(ram)) {
 		return ram[address];
 	}
-	// TODO: serial interface, 0xa000-0xbfff
-	// TODO: ROM, 0xc000-0xffff
+
+	// ROM
+	if (address >= 0xc000) {
+		const uint8_t *rom = &_binary____osi_bas_ROM_o_bin_start;
+
+		return rom[address - 0xc000];
+	}
 
 	return 0xff;
 }

src/rom.h

@@ -0,0 +1,5 @@
+
+// Symbols exported by rom.o, see https://balau82.wordpress.com/2012/02/19/linking-a-binary-blob-with-gcc/
+extern unsigned char _binary____osi_bas_ROM_o_bin_end;
+extern unsigned char _binary____osi_bas_ROM_o_bin_size;
+extern unsigned char _binary____osi_bas_ROM_o_bin_start;