M68ICS08GR datasheet(404/408 Pages) FREESCALE

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Glossary

Technical Data

MC68HC908GR8 — Rev 4.0

404

Glossary

MOTOROLA

timer interface module (TIM) — A module used to relate events in a system to a point in time.

timer — A module used to relate events in a system to a point in time.

toggle — To change the state of an output from a logic 0 to a logic 1 or from a logic 1 to a logic 0.

tracking mode — Mode of low-jitter PLL operation during which the PLL is locked on a

frequency. Also see "acquisition mode."

two’s complement — A means of performing binary subtraction using addition techniques. The

most significant bit of a two’s complement number indicates the sign of the number (1

indicates negative). The two’s complement negative of a number is obtained by inverting

each bit in the number and then adding 1 to the result.

unbuffered — Utilizes only one register for data; new data overwrites current data.

unimplemented memory location — A memory location that is not used. Writing to an

unimplemented location has no effect. Reading an unimplemented location returns an

unpredictable value. Executing an opcode at an unimplemented location causes an illegal

address reset.

V —The overflow bit in the condition code register of the CPU08. The CPU08 sets the V bit when

a two's complement overflow occurs. The signed branch instructions BGT, BGE, BLE,

and BLT use the overflow bit.

variable — A value that changes during the course of program execution.

VCO — See "voltage-controlled oscillator."

vector — A memory location that contains the address of the beginning of a subroutine written

to service an interrupt or reset.

voltage-controlled oscillator (VCO) — A circuit that produces an oscillating output signal of a

frequency that is controlled by a dc voltage applied to a control input.

waveform — A graphical representation in which the amplitude of a wave is plotted against time.

wired-OR — Connection of circuit outputs so that if any output is high, the connection point is

high.

word — A set of two bytes (16 bits).

write — The transfer of a byte of data from the CPU to a memory location.

X — The lower byte of the index register (H:X) in the CPU08.

Z — The zero bit in the condition code register of the CPU08. The CPU08 sets the zero bit when

an arithmetic operation, logical operation, or data manipulation produces a result of $00.

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