Initial commit

design.txt

@@ -0,0 +1,81 @@
+
+* 8 16-bit registers
+
+* Memory
+	4096 bytes. address aligned by 2 bytes (16 bit)
+
+
+* instruction set (16 bit)
+
+0001 - add
+0010 - movl (move low byte)
+0011 - movh (move high byte)
+0100 - load word
+0101 - store word
+0110 - beq
+0111 - jmp
+1000 - jr (jump register)
+
+1111 - I/O Write
+
+I/O = only 8 bits, syscall?
+
+--- Format ---
+
+Register operation format (R):
+
+	opcode (4) | rs (4)  | r0 (4) | r1 (4)
+
+	r0,r1 	- Operand registers.
+	rs   	- save register
+
+Register operation format (RI):
+
+	opcode (4) | rs (4)  | r0 (4) | offset (signed 4)
+
+	r0 	- Operand registers.
+	offset  - constant offset from r0 value.
+	rs   	- save register
+
+Constant operation format (I):
+
+	opcode (4) | reg (4) | data (signed 8)
+
+	reg - Register
+	data - Constant data to insert into reg.
+
+Jump format (J):
+
+	opcode (4) | addr (signed 12)
+
+
+
+* load ascii hex from file.
+* jump, branch instructions
+
+start:
+add r0, r4 # r4 = 1
+
+beq r0, r1
+jmp 2
+jmp 3
+load r3
+jr r3
+write r0
+
+
+if (r0 == r1)
+	jmp(b1);
+else
+	jmp(b2);
+b1:
+	load(r3);
+	jmpl(r3);
+b2:
+	write(r0);
+
+
+while (r0 == r1)
+	r0++;
+
+beq r0 r1 #