Analog Devices Blackfin ADSP-BF537 Hardware Reference Manual page 1155

Glossary
PWM (Pulse Width Modulation).
Also called Pulse Duration Modulation (PDM), PWM is a pulse modula-
tion technique in which the duration of the pulses is varied by the
modulating voltage.
RAS (Row Address Strobe).
A signal sent from the SDC to a DRAM device to indicate validity of row
address lines.
Real-Time Clock (RTC).
A component that generates timing pulses for the digital watch features of
the processor, including time of day, alarm, and stopwatch countdown
features.
ROM (Read-Only Memory).
A data storage device manufactured with fixed contents. This term is most
often used to refer to non-volatile semiconductor memory.
RTC.
See Real-Time Clock
RZ (Return-to-Zero modulation).
A binary encoding scheme in which two signal pulses are used for every
bit. A 0 is represented by a change from the low voltage level to the high
voltage level; a 1 is represented by a change from the high voltage level to
the low voltage level. A return to a reference (0) voltage is made between
encoded bits.
ADSP-BF537 Blackfin Processor Hardware Reference G-19