Dolby Laboratories DP503 - Manual (Page 68)

A-4
A.2 RS-449 Interface Description
A.2.1 Functional Description
The Dolby DP503 provides a standard RS-449 interface in the type DT mode (data
and timing signals only, no handshakes) through a 37-pin female D-connector.
RS-449 is the mechanical specification for a balanced (differential) transmission
system meeting RS-422 and RS-423 electrical specifications. The Model DP503 is
configured as data terminal equipment (DTE), and is typically connected to data
circuit-terminating equipment (DCE). The DP503 encoder provides a reference
clock at the target data rate on the terminal timing (TT) pins, receives a data clock
from a DCE device on the send timing (ST) pins, and transmits data on the send
data (SD) pins. The internal timing and sample clocks of the DP503 are phase-
locked to ST and RT, respectively. In addition to these differential signals, the
connector also provides pins for signal and chassis ground. The connector pinout
is given in Section 8.1.4 above.
A.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