[1] COP400 family members are complete microcomputers containing internal timing, logic, ROM, RAM, and I/O necessary to implement dedicated controllers.

Due to the special characteristics associated with the JP and JSRP instructions, ROM must often be conceived of as organized into pages of 64 bytes each.

Also, because of the unique operations performed by the LQID and JID instructions, ROM pages must sometimes be thought of as organized into blocks of 256 bytes.

Some low end family members omit the SC stack register.

It can also be used to load the Br and Bd portions of the B register, to load and input 4 bits of the 8-bit Q latch data, to input 4 bits of the 8-bit L port and to perform data exchanges with the SIO register.

The value of PC is automatically incremented by 1 prior to the execution of the current instruction to point to the next sequential ROM location.

This example code demonstrates several of the space saving features on the instruction set: Early COP400 devices that have 28 pins or more support a single interrupt.

Interrupt is enabled by setting bit 1 of the EN register to 1 with a LEI instruction.

The PC is then pushed on the subroutine stack and control is transferred to the interrupt handler at address 0xFF.

Subroutines are supported inside interrupt service routines on devices with a stack pointer.

Dual CPU, a deeper stack in RAM, and larger address spaces were added to some devices by 1985.

These single-chip barrel processors contain two ostensibly independent CPUs that share instructions, memory, and most IO devices.

In reality, the CPUs are not fully independent and share hardware resources similar to Intel processors with Hyper-Threading Technology (HTT).

The so-called group 4 devices extended the memory limit by adding three-byte JMP, JSR, and LBI instructions with more address bits.

T400 is intended to be a replacement for the original chip in SOCs recreating legacy systems.

[13] There is an open-source MAME emulator for the COP400 family and several hand held games and specialty calculators.