MC68HC908EY16 Datasheet, PDF (259/278 Pages) Motorola, Inc – Microcontrollers

Glossary
A — See “accumulator (A).”
accumulator (A) — An 8-bit general-purpose register in the CPU08. The CPU08 uses the accumulator
to hold operands and results of arithmetic and logic operations.
acquisition mode — A mode of PLL operation during startup before the PLL locks on a frequency. Also
see "tracking mode."
address bus — The set of wires that the CPU or DMA uses to read and write memory locations.
addressing mode — The way that the CPU determines the operand address for an instruction. The
M68HC08 CPU has 16 addressing modes.
ALU — See “arithmetic logic unit (ALU).”
arithmetic logic unit (ALU) — The portion of the CPU that contains the logic circuitry to perform
arithmetic, logic, and manipulation operations on operands.
asynchronous — Refers to logic circuits and operations that are not synchronized by a common
reference signal.
baud rate — The total number of bits transmitted per unit of time.
BCD — See “binary-coded decimal (BCD).”
binary — Relating to the base 2 number system.
binary number system — The base 2 number system, having two digits, 0 and 1. Binary arithmetic is
convenient in digital circuit design because digital circuits have two permissible voltage levels, low and
high. The binary digits 0 and 1 can be interpreted to correspond to the two digital voltage levels.
binary-coded decimal (BCD) — A notation that uses 4-bit binary numbers to represent the 10 decimal
digits and that retains the same positional structure of a decimal number. For example,
234 (decimal) = 0010 0011 0100 (BCD)
bit — A binary digit. A bit has a value of either 0 or 1.
branch instruction — An instruction that causes the CPU to continue processing at a memory location
other than the next sequential address.
break module — A module in the M68HC08 Family. The break module allows software to halt program
execution at a programmable point in order to enter a background routine.
breakpoint — A number written into the break address registers of the break module. When a number
appears on the internal address bus that is the same as the number in the break address registers,
the CPU executes the software interrupt instruction (SWI).
MC68HC908EY16 • MC68HC908EY8 Data Sheet, Rev. 10
Freescale Semiconductor
259