Instruction manual

ACU-1000 Operations Manual
5-6 Interoperability Now
5.7 DSP-2 Module
5.7.1 General Description DSP-2
The DSP-2 module is another type of 4-wire interface module. It is like the RDI-1 module in
that it is used to interface radios and other 4-wire devices, but it contains functions the RDI-1
does not, such as three types of COR sensing: hardwired signal, VMR, and VOX. It offers a
DSP noise reduction mode. Its VMR and noise reduction capability make it an ideal interface
for HF radios. In addition, it also contains an Ethernet port for network connectivity functions
similar to the NXU-2.
5.7.2 Block Diagram Description DSP-2
(Refer to Figure 5-2 DSP-2 Block Diagram)
The DSP-2 module has been redesigned for single board construction to include the DSP
functions on a single printed board instead of a plug on DSP subassembly. In addition, network
functions have been added to allow the DSP-2 to function as either a standalone NXU-2 type
device for network connectivity, or as a hybrid device to allow a network interface device to
have access to the backplane audio buses. An Ethernet connector is included on the front panel
for connection to a TCP/IP type network. A Link Active LED on the front panel turns ON
when a network connection has been established.
The function of the DSP-2 module is to connect four wire transmit and receive audio to the 16-
line audio bus structure on the ACU main chassis backplane board. Receive audio is routed to
the audio buses by audio gates U17 through U26, and send audio is brought in from the audio
buses by audio gates U17 through U25. These audio gates are controlled directly by a
Programmable Logic Device (PLD), U7, which receives instructions directly from the DSP
processor, U10. The DSP processor, U10, in turn, receives its instructions from the CPM-4
module in the system via I/O latches and drivers located in PLD, U7. Thus, the connections to
and from any audio bus are controlled ultimately by the CPM-4 module, which decides which
buses to assign to the DSP-2 module depending on a number of system parameters. The CPM-
4 passes connect information to the DSP processor on the DSP-2 module, which controls the
audio gates.
Audio from an audio bus is routed to the transmit output through amplifier U16A, then through
amplifier U12B. The course output level is set via gain select switches which are controlled by
the DSP processor. Fine level set is done via the DSP software controls. Receive audio in is
routed through amplifier U15A,B, then through amplifier U16B, which is gain-controlled by
DSP switches, and then into the A/D input on U8. The DSP processor processes the audio and
outputs its signal onto an audio bus through audio gates U17 through U26. The DSP software
module runs a DTMF receiver, which decodes the DTMF digits that may come in from a
receiver and passes them digitally on to the system’s CPM-4 for processing. Under instructions
from the CPM-4, the DSP-2 module generates DTMF signals, which are routed to the transmit
output through amplifier U12B.