Instruction Summary

This is a summary of 4004 instructions.

Abbreviations used are as follows:

Abbreviation	Description
A	Accumulator.
A n	Bit n in the accumulator, where n may have any value from 0 to 3.
ADDR	A read-only memory or program random-access memory address.
carry	The carry bit.
PC	The 12-bit Program Counter.
PCH	The high-order 4 bits of the Program Counter.
PCL	The low-order 4 bits of the Program Counter.
PCM	The middle 4 bits of the Program Counter.
RAM	Random Access Memory.
REG	Any index register from 0 to 15.
R0	Index Register 0.
R1	Index Register 1.
ROM	Read Only Memory.
RP	Any index register pair from 0P to 7P.
STK	The address stack
	The number obtained by complementing each bit of “value”.
X:Y	The value obtained by concatenating the values X and Y.
[ ]	An optional field enclosed by brackets.
( )	Contents of register or memory enclosed by parentheses.
	Replace value on left hand side of arrow with value on right hand side.

Instruction Summary

Group	Definition
Index Register Instructions	Instructions which involve index registers or register pairs.
Index Register to Accumulator Instructions	Instructions which involve an operation between an index register and the accumulator. Instructions in this class occupy one byte.
Accumulator Instructions	Instructions which operate only on the contents of the accumulator and/or the carry bit. Instructions in this class occupy one byte.
Immediate Instructions	Instructions which use data that is part of the instruction itself.
Transfer Of Control Instructions	Instructions which alter the normal execution sequence of instructions.
Subroutine Linkage Instructions	Instructions which call and cause return from subroutines. They cause a transfer of program control and use the address stack.
No-Operation Instruction	This instruction occupies one byte.
Memory Selection Instructions	Instructions which specify DATA RAM data and status characters, RAM output ports and ROM input and output ports to be operated on by I/O and RAM instructions
Input/Output and RAM Instructions	Instructions which access DATA RAM characters or perform input or output operations. One instruction, WPM, allows the programmer to read or write 8-bit program RAM locations. These instructions use addresses selected by the DCL and SRC instructions.