Added mapped memory for display

1 files changed, 23 insertions, 8 deletions

diff --git a/lc3.c b/lc3.c
index 5dc7112..250ca06 100644
--- a/lc3.c
+++ b/lc3.c
@@ -64,9 +64,14 @@ enum Trap
 	TRAP_HALT = 0x25,
 };
 
-const uint16_t PC_START = 0x3000;
-const uint16_t KBSR = 0xfe00;
-const uint16_t KBDR = 0xfe02;
+enum Memory
+{
+	MEMORY_START = 0x3000,
+	MEMORY_KBSR = 0xfe00,
+	MEMORY_KBDR = 0xfe02,
+	MEMORY_DSR = 0xfe04,
+	MEMORY_DDR = 0xfe06,
+};
 
 uint16_t memory[UINT16_MAX];
 uint16_t registers[REGISTER_COUNT];
@@ -127,23 +132,33 @@ uint16_t check_key()
 
 uint16_t read_memory(const uint16_t address)
 {
-	if (address == KBSR)
+	if (MEMORY_KBSR == address)
 	{
 		if (check_key())
 		{
-			memory[KBSR] = 1u << 15;
-			memory[KBDR] = getchar();
+			memory[MEMORY_KBSR] = 1u << 15;
+			memory[MEMORY_KBDR] = getchar();
 		}
 		else
 		{
-			memory[KBSR] = 0;
+			memory[MEMORY_KBSR] = 0;
 		}
 	}
+	else if (MEMORY_DSR == address)
+	{
+		memory[MEMORY_DSR] = 1u << 15;
+	}
 	return memory[address];
 }
 
 void write_memory(const uint16_t address, const uint16_t value)
 {
+	if (MEMORY_DDR == address)
+	{
+		uint8_t c = (uint8_t) value;
+		ssize_t r = write(1, &c, 1);
+		die(r, "write_memory write()");
+	}
 	memory[address] = value;
 }
 
@@ -401,7 +416,7 @@ int main(int argc, char ** argv)
 	signal(SIGINT, handle_interrupt);
 	atexit(restore_terminal);
 	prepare_terminal();
-	registers[REGISTER_PC] = PC_START;
+	registers[REGISTER_PC] = MEMORY_START;
 	for (;;)
 	{
 		const uint16_t instruction = read_memory(registers[REGISTER_PC]++);