
MOTOROLA
ii
MC68HC05B6
GLOSSARY
EVS
Evaluation system. One of the range of platforms provided by Motorola for
evaluation and emulation of their devices.
HCMOS
High-density complementary metal oxide semiconductor. A semiconductor
technology chosen for its low power consumption and good noise immunity.
I/O
Input/output; used to describe a bidirectional pin or function.
Input capture
(IC) This is a function provided by the timing system, whereby an external
event is ‘captured’ by storing the value of a counter at the instant the event
is detected.
Interrupt
This refers to an asynchronous external event and the handling of it by the
MCU. The external event is detected by the MCU and causes a
predetermined action to occur.
IRQ
Interrupt request. The overline indicates that this is an active-low signal
format.
K byte
A kilo-byte (of memory); 1024 bytes.
LCD
Liquid crystal display.
LSB
Least signicant byte.
M68HC05
Motorola’s family of 8-bit MCUs.
MCU
Microcontroller unit.
MI BUS
Motorola interconnect bus. A single wire, medium speed serial
communications protocol.
MSB
Most signicant byte.
Nibble
Half a byte; four bits.
NRZ
Non-return to zero.
Opcode
The opcode is a byte which identies the particular instruction and operating
mode to the CPU. See also: prebyte, operand.
Operand
The operand is a byte containing information the CPU needs to execute a
particular instruction. There may be from 0 to 3 operands associated with an
opcode. See also: opcode, prebyte.
Output compare
(OC) This is a function provided by the timing system, whereby an external
event is generated when an internal counter value matches a predened
value.
PLCC
Plastic leaded chip carrier package.
PLL
Phase-locked loop circuit. This provides a method of frequency
multiplication, to enable the use of a low frequency crystal in a high
frequency circuit.
Prebyte
This byte is sometimes required to qualify an opcode, in order to fully specify
a particular instruction. See also: opcode, operand.
TPG
278
05B6Book Page ii Tuesday, April 6, 1999 8:24 am