Dolby Laboratories DP503 - Manual (Page 32)

4-2
AES and IEC convention calls for XLR pin 2 to be “high/hot” and pin 3 to be
“low/cold.” In the interests of maintaining international standardization, we suggest
that the AES and IEC recommendations be followed.
In an installation where the source is unbalanced, avoid ground loops by using two
conductor shielded cable exactly as for balanced circuits; in other words, ensure
that the unbalancing (connecting the wire to pin 3 to ground) occurs only at the end
remote from the Model DP503. Note that both audio pins of the XLRs (pins 2 and
3) must be connected; neither may be left open.
4.3 Data / Status / Control Connections
4.3.1 Encoded Data Out and Timing
Note If you are using the DP503 as part of a Dolby Fax system, substitute the information provided in
Section 4.4 below.
The data output connection occurs at the 37-pin D-connector J105 Encoded Data
Out and Timing.
This connector follows the interface specifications of EIA standard RS-449 in the
type DT mode (data and timing signals only). Under RS-449, the DP503 is
categorized as data terminal equipment (DTE), and is typically connected to data
circuit-terminating equipment (DCE). Detailed information on the RS-449
interface is provided in Appendix A.
System Clock Requirements
A phase-locked loop (PLL) generates all sample and data timing. The PLL locks to an external data clock at
the target data rate, and a crystal-based oscillator is used within the PLL to minimize timing jitter in
the sampled audio data. The frequency locking range of the loop is
H 100 ppm of the target bit rate.
This requires a stable external data clock with a 50% duty cycle per RS-449 specifications.
For those applications that lack a suitable external data clock, the DP503 provides a reference clock for system
timing (RS-449 TT signal); this clock has been trimmed to an accuracy of
H 25 ppm with respect to
the target bit rate.
4.3.2 Auxiliary Data
If required, make auxiliary data connections to the 9-pin D connector J106
Aux/Acc.
This connector follows the interface specifications of EIA standard RS-232, with a
minimum 2-wire connection (half-duplex). The auxiliary data channel supports a
10-bit asynchronous serial data format (1 start bit, 1 stop bit, 8 data bits, no parity)
at a data rate specified by the user. Under RS-232, the Model DP503 is categorized
as a DCE device, and typically connected to data terminal equipment (DTE).
Detailed information on the RS-232 interface is provided in Appendix A.
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