MC68HC908MR8 Datasheet, PDF (363/372 Pages) Motorola, Inc – Microcontrollers

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 non-existent 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.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
363