Dolby Laboratories DP524 - Manual (Page 29)

6-3
6.2 RS-449 Interface Description
6.2.1 Functional Description
The Dolby Model DP524 provide a standard RS-449 interface in the type DT mode
(data and timing signals only, no handshakes) through 37-pin male D-connectors.
RS-449 is the mechanical specification for a balanced (differential) transmission
system meeting RS-422 and RS-423 electrical specifications. The Model DP524 is
configured as data terminal equipment (DTE), and are typically connected to data
circuit-terminating equipment (DCE) such as RF modems. The DP524 decoder
receives a data clock from a DCE device on the receive timing (RT) pins, and
receives data on the receive data (RD) pins. The internal timing and sample clocks
of the DP524 are phase-locked to ST and RT, respectively. In addition to these
differential signals, the connector also provides pins for signal and chassis ground;
connector pinout is given in the section above. No other RS-449 signals are
supported in these units.
6.2.2 Interface Timing
A “mark,” or “off” state is said to exist when the “+” side of a signal is at a lower
potential than the corresponding “-” side. A “space,” or “on” state exists when the
opposite condition is true. The following timing diagram shows the relationship
between clock and signal lines:
TT
ST
on
off
SD
RT
RD
MAIN