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Theory of Operation
3–30
AM700 Audio Measurement Set Service Manual
limited to about 150 mA. Digital devices requiring more power than available
from these sources may be powered by an external power source.
The DSP port timing diagram is shown in Figure 3–9. The external device
determines the sampling rate. The sampling rate to the AM700 must be no
greater than 48 kHz, and the data must be 16-bit. Bit and Frame Clocks must
always be “clean,” with no extra transitions, while the AM700 is in DSP mode.
For this reason, the AM700 should be set to AES mode when switching the
sample rate of any external device attached to the DSP port. The maximum input
voltage for the DSP port is –0.5 V to +5.5 V. For good noise immunity, the rise
and fall time of the transitions should be less than 100 ns.
NOTE. The DSP generator must also be selected to permit the DSP to acquire
input from the DSP port.
8 7 6 5 4 3 2 1
15 14 13 12 11 10 9
DB-15 FEMALE CONNECTOR
DSP Port
Pin 1 Bit Clock
Pin 2 Receive Data
Pin 3 Transmit Data
Pin 4 Rate 2
Pin 5 Rate 1
Pin 6 Rate 0
Pin 7 +12V
Pin 8 –12V
Pin 9 Chassis Ground
Pin 10 Chassis Ground
Pin 11 Chassis Ground
Pin 12 Frame Sync
Pin 13 Flag 1
Pin 14 Flag 0
Pin 15 Chassis Ground
Figure 3–9: Digital signal processor port connector
NOTE. In order to meet radiated EMI regulations, the cable used to connect to
the DSP port must be well shielded, and the connector housing must be
conductive. The cable shield must be clamped by the housing where the cable
enters the connector.