My CPU

Data

Memory Adress

An 16 bit address for a location in memory. This uses the the "data" area of an instruction

Registers

General purpose registers addresses are a number in the range of 0-7 with the prefix 'R'. This is in 8 bits.

Example: R7

Result: 00000111 (0x07)

Instructions

An instruction is made up of a 16 bit opcode and has two paramaters.

• Paramater one (P1) An 8 bit data format normaly used for a register address.

• Paramater two (P2) A 16 bit data format normally split into an upper byte (P2 U) and a lower byte (P2 L).

You may use the assembler to assemble a program for the CPU.

Load a value into a register

Example: LD R1, 0xabcd

Result:

Opcode	P1	P2 U	P2 L
0x0000	0x01	0xab	0xcd

Combined Result: 0x000001abcd

Load the value of a register into another register

Example: LD R1, R2

Result:

Opcode	P1	P2 U	P2 L
0x0001	0x01	0x00	0x02

Combined Result: 0x0001010002

Load the value from memory into a register

Example: LD R1, $0xABCD

Result:

Opcode	P1	P2 U	P2 L
0x0002	0x01	0xab	0xcd

Combined Result: 0x000201abcd

A simplified table for all instructions.

EXAMPLE	OPCODE	P1	P2 U	P2 L
LD R1, 0xabcd	0x0000	A register	0xAB	0xCD
LD R1, R2	0x0001	A register	0x00	A register
LD R1, $0xABCD	0x0002	A register	0xAB	0xCD
ST R1, $0xABCD	0x0010	A register	0xAB	0xCD
STL R1, $0xABCD	0x0011	A register	0xAB	0xCD
STH R1, $0xABCD	0x0012	A register	0xAB	0xCD
ST R1, R2	0x0013	A register	0x00	A register
STL R1, R2	0x0014	A register	0x00	A register
STH R1, R2	0x0015	A register	0x00	A register
CMP R1, R2	0x0020	A register	0x00	A register
CMP R1, 0xabcd	0x0021	A register	0xAB	0xCD
JEQ label	0x0030	0x00	0xAB	0xCD
JGT label	0x0031	0x00	0xAB	0xCD
JLT label	0x0032	0x00	0xAB	0xCD
JMP label	0x0033	0x00	0xAB	0xCD
ADD R1, 0xabcd	0x0040	A register	0xAB	0xCD
SUB R1, 0xabcd	0x0041	A register	0xAB	0xCD
ADD R1, R2	0x0042	A register	0x00	A register
SUB R1, R2	0x0043	A register	0x00	A register
HALT	0xFFFE	0xFF	0xFF	0xFF
NOOP	0xFFFF	0xFF	0xFF	0xFF