
Glossary
Advance Information
MC68HC08AZ60A
—
Rev 0.0
472
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.