Glossary - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 829

Glossary

Accumulator A register in a computer that contains an operand to be used in an arithmetic

operation.
Acknowledgement error An error detected whenever the transmitter does not monitor a
dominant bit in the ACK slot in a CAN bus protocol.
Activation record Another term for stack frame.
Address access time The amount of time it takes for a memory component to send out valid
data to the external data pins after address signals have been applied (assuming that all
other control signals have been asserted).
Addressing Applying a unique combination of high and low logic levels to select a corresponding
unique memory location.
Address multiplexing A technique that allows the same address pin to carry different
signals at different times; used mainly by DRAM technology. Address multiplexing can
dramatically reduce the number of address pins required by DRAM chips and the size of the
memory chip package.
Algorithm A set of procedure steps represented in pseudo-code that is designed to solve
certain computation issues.
Arithmetic logic unit (ALU) The part of the processor in which all arithmetic and logical

operations are performed.
Array An ordered set of elements of the same type. The elements of the array are arranged
so that there is a zeroth, first, second, third, and so forth. An array may be one-, two-, or
multidimensional.
American Standard Code for Information Interchange (ASCII) A code that uses 7 bits to

encode all printable and control characters.
Assembler A program that converts a program in assembly language into machine instructions
so that it can be executed by a computer.
Assembler directive A command to the assembler for defining data and symbols, setting
assembling conditions, and specifying output format. Assembler directives do not produce
machine code.
Assembly instruction A mnemonic representation of a machine instruction.
Assembly program A program written in assembly language.
Automatic variable A variable defined inside a function that comes into existence when the
function is entered and disappears when the function returns.
Background receive buffer The receive buffer where the incoming frame is placed before it is
forwarded to the foreground receive buffer.
Barometric pressure The air pressure existing at any point within the Earth's atmosphere.
BDM mode A mode provided by the HCS12 and some other Freescale microcontrollers
to facilitate the design of debugging tools. This mode has been utilized to implement
source-level debuggers.
Binary Coded Decimal (BCD) Four binary digits representing a decimal digit. The binary
codes 0000 2 -1001 2 correspond to the decimal digits 0 to 9.
Bit error An error interpreted in the CAN bus protocol by a node sending a bit on the
bus when it monitors the bus and detects a bit value that is different from the bit value
being sent.