M68ICS08GR datasheet(398/408 Pages) FREESCALE

398 / 408 page

Glossary

Technical Data

MC68HC908GR8 — Rev 4.0

398

Glossary

MOTOROLA

direct memory access module (DMA) — A M68HC08 Family module that can perform data

transfers between any two CPU-addressable locations without CPU intervention. For

transmitting or receiving blocks of data to or from peripherals, DMA transfers are faster

and more code-efficient than CPU interrupts.

DMA — See "direct memory access module (DMA)."

DMA service request — A signal from a peripheral to the DMA module that enables the DMA

module to transfer data.

duty cycle — A ratio of the amount of time the signal is on versus the time it is off. Duty cycle is

usually represented by a percentage.

EEPROM — Electrically erasable, programmable, read-only memory. A nonvolatile type of

memory that can be electrically reprogrammed.

EPROM — Erasable, programmable, read-only memory. A nonvolatile type of memory that can

be erased by exposure to an ultraviolet light source and then reprogrammed.

exception — An event such as an interrupt or a reset that stops the sequential execution of the

instructions in the main program.

external interrupt module (IRQ) — A module in the M68HC08 Family with both dedicated

external interrupt pins and port pins that can be enabled as interrupt pins.

fetch — To copy data from a memory location into the accumulator.

firmware — Instructions and data programmed into nonvolatile memory.

free-running counter — A device that counts from zero to a predetermined number, then rolls

over to zero and begins counting again.

full-duplex transmission — Communication on a channel in which data can be sent and

received simultaneously.

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

H — The half-carry bit in the condition code register of the CPU08. This bit indicates a carry from

the low-order four bits of the accumulator value to the high-order four bits. The half-carry

bit is required for binary-coded decimal arithmetic operations. The decimal adjust

accumulator (DAA) instruction uses the state of the H and C bits to determine the

appropriate correction factor.

hexadecimal — Base 16 numbering system that uses the digits 0 through 9 and the letters A

through F.

high byte — The most significant eight bits of a word.

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M68ICS08GR Datasheet(PDF) 398 Page - Freescale Semiconductor, Inc