MC68HC908EY16 Datasheet, PDF (262/278 Pages) Motorola, Inc – Microcontrollers

Glossary
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.
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).
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
262
Freescale Semiconductor