Dolby Laboratories DP524 - Manual (Page 22)

4-2
For optimum immunity to radio-frequency interference, cable shields must be
connected to the shells of the XLR connectors, not to pin 1.
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 DP524. Note that both audio pins of the XLRs (pins 2 and
3) must be connected; neither may be left open.
4.3 Data, Status, and Remote Control Connections
Note Serial Command control can also be implemented in specialized applications by means of the RS-
232 port, J105). See Section 6.3.
4.3.1 Encoded Data In & Timing - J103
Make the Encoded Data In and Timing connections to the 37-pin D-connector
J103. 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 DP524 is
categorized as data terminal equipment (DTE), and is typically connected to data
circuit-terminating equipment (DCE) such as telecommunications or RF modems.
Detailed information on the RS-449 interface is provided in Section 6.2.
System Clock Requirements
A phase-locked loop (PLL) generates all sample and data timing. The PLL locks to
an external data clock at the coder 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
±
100 ppm. As an example, a 192kHz data rate would
require a stable external data clock in the range from 191.9808 kHz to 192.0192
kHz, with a 50% duty cycle per RS-449.
4.3.2 RS-232 (J105)
The RS-232 connection can be used for three purposes:
a. As an input for downloading software upgrades; see Section 5.4.
b. As an I/O port for remote commands. See Section 8.
c. As an output for auxiliary data sent from the encoder and embedded
in the digital audio data stream. RS-232 interface data can be found in
Section 7.1. The Command/Aux data switch (S101-4) should be in the
Down position. The communications protocol for command mode is fixed at
1 stop bit, no parity and the baud rate is set as follows:
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