Glossary - The HCS12/9S12: An Introduction to Software and Hardware Interfacing - page 834

Machine instruction A set of binary digits that tells the computer what operation to perform.
Mark A term used to indicate a binary 1.
Maskable interrupts Interrupts that can be ignored by the CPU. This type of interrupt can be
disabled by setting a mask bit or by clearing an enable bit.
Masked ROM (MROM) A type of ROM that is programmed when the chip is manufactured.
Matrix A two-dimensional data structure that is organized into rows and columns. The
elements of a matrix are of the same length and are accessed using their row and column
numbers ( i , j ), where i is the row number and j is the column number.
Memory Storage for software and information.
Memory capacity The total amount of information that a memory device can store; also
called memory density.
Memory organization A description of the number of bits that can be read from or written
into a memory chip during a read or write operation.
Microcontroller A computer system implemented on a single, very-large-scale integrated
circuit. A microcontroller contains everything that is in a microprocessor and may contain
memories, an I/O device interface, a timer circuit, an A/D converter, and so on.
Microprocessor A CPU packaged in a single integrated circuit.
Mode fault An SPI error that indicates that there may have been a multimaster conflict for
system control. Mode fault is detected when the master SPI device has its SS pin pulled low.
Modem A device that can accept digital bits and change them into a form suitable for analog
transmission (modulation) and can also receive a modulated signal and transform it back to
its original digital representation (demodulation).
Multidrop A data communication scheme in which more than two stations share the same data
link. One station is designated as the master, and the other stations are designated as slaves.
Each station has its own unique address, with the primary station controlling all data transfers
over the link.
Multiprecision arithmetic Arithmetic operations (add, subtract, multiply, or divide) performed
by a computer that deals with operands longer than the computer's word length.
Multitasking A computing technique in which CPU time is divided into slots that are
usually 10 to 20 ms in length. When multiple programs are resident in the main memory
waiting for execution, the operating system assigns a program to be executed to one time
slot. At the end of a time slot or when a program is waiting for completion of I/O, the
operating system takes over and assigns another program to be executed.
Nibble A group of 4-bit information.
Nonmaskable interrupts Interrupts that the CPU cannot ignore.
Nonvolatile memory Memory that retains stored information even when power to the
memory is removed.
Null modem A circuit connection between two DTEs in which the leads are interconnected
in such a way as to fool both DTEs into thinking that they are connected to modems. A null
modem is only used for short-distance interconnections.
Object code The sequence of machine instructions that results from the process of assembling
and/or compiling a source program.
Output-compare An HCS12 timer function that allows the user to make a copy of the value
of the 16-bit main timer, add a delay to the copy, and then store the sum in a register. The
output-compare function compares the sum with the main timer in each of the following
E-clock cycles. When these two values are equal, the circuit can trigger a signal change on
an output-compare pin and may also generate an interrupt request to the HCS12.