M68ICS08GR datasheet(399/408 Pages) FREESCALE

399 / 408 page

Glossary

MC68HC908GR8 — Rev 4.0

Technical Data

MOTOROLA

Glossary

399

illegal address — An address not within the memory map

illegal opcode — A nonexistent opcode.

I — The interrupt mask bit in the condition code register of the CPU08. When I is set, all interrupts

are disabled.

index register (H:X) — A 16-bit register in the CPU08. The upper byte of H:X is called H. The

lower byte is called X. In the indexed addressing modes, the CPU uses the contents of

H:X to determine the effective address of the operand. H:X can also serve as a temporary

data storage location.

input/output (I/O) — Input/output interfaces between a computer system and the external world.

A CPU reads an input to sense the level of an external signal and writes to an output to

change the level on an external signal.

instructions — Operations that a CPU can perform. Instructions are expressed by programmers

as assembly language mnemonics. A CPU interprets an opcode and its associated

operand(s) and instruction.

interrupt — A temporary break in the sequential execution of a program to respond to signals

from peripheral devices by executing a subroutine.

interrupt request — A signal from a peripheral to the CPU intended to cause the CPU to

execute a subroutine.

I/O — See “input/output (I/0).”

IRQ — See "external interrupt module (IRQ)."

jitter — Short-term signal instability.

latch — A circuit that retains the voltage level (logic 1 or logic 0) written to it for as long as power

is applied to the circuit.

latency — The time lag between instruction completion and data movement.

least significant bit (LSB) — The rightmost digit of a binary number.

logic 1 — A voltage level approximately equal to the input power voltage (V

DD).

logic 0 — A voltage level approximately equal to the ground voltage (V

SS).

low byte — The least significant eight bits of a word.

low voltage inhibit module (LVI) — A module in the M68HC08 Family that monitors power

supply voltage.

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M68ICS08GR Datasheet(PDF) 399 Page - Freescale Semiconductor, Inc