Technical Manual
Table Of Contents
- Vocoder and Controller Boards Detailed Theory of Operation
- Introduction to This Section
- General
- Vocoder Board
- Controller Board
- Switching Regulator
- RX Signal Path
- TX Signal Path
- Controller Bootstrap and Asynchronous Buses
- Vocoder Bootstrap
- SPI Bus Interface
- Universal Connector and Option Selects
- Keypad and Display Module
- Controls and Control Top Flex
- Controller Memory Map
- Vocoder Memory Map
- MCU System Clock
- DSP System Clock
- Radio Power-Up/ Power-Down Sequence
- Notes
- Secure Modules
- Disassembly/Reassembly Procedures
- Troubleshooting Procedures
- Troubleshooting Charts
- Troubleshooting Waveforms
- Troubleshooting Diagrams
6-6
RX Signal Path
The vocoder processes all received signals digitally. This requires a
unique back end from a standard analog radio. This unique
functionality is provided by the ABACUS IC, with the ADSIC (U406)
acting as the interface to the DSP. The ABACUS IC, located on the
transceiver board, provides a digital back end for the receiver section.
It provides a digital output of I (in phase) and Q (quadrature) data
words that represent the IF (Intermediate Frequency) signal at the
receiver back end (refer to appropriate transceiver section for more
details on ABACUS operation). This data is passed to the DSP via an
interface with the ADSIC (U406) for appropriate processing.
The ADSIC interface with the ABACUS comprises the four signals: SBI,
DIN, DIN*, and ODC (refer to Figure 9).
NOTE:
An asterisk symbol (*) next to a signal name
indicates a negative or NOT logic true signal.
SBI
is a programming data line for the ABACUS. This line is used to
configure the operation of the ABACUS, and is driven by the ADSIC.
The MCU programs many of the ADSIC operational features through
the SPI interface. There are 36 configuration registers in the ADSIC, of
which four contain configuration data for the ABACUS. When these
particular registers are programmed by the MCU, the ADSIC in turn
sends this data to the ABACUS through the SBI.
DIN and DIN*
are the data lines in which the I and Q data words are
transferred from the ABACUS. These signals make up a differentially
encoded current loop. Instead of sending TTL-type voltage signals, the
data is transferred by flowing current one way or the other through the
loop. This helps reduce internally generated spurious emissions on the
transceiver board. The ADSIC contains an internal current loop
decoder which translates these signals back to TTL logic and stores the
data in internal registers.
48KHz TX Data Interrupt
Serial Transmit Data
Serial Receive Data
2.4 MHz Receive Data Clock
20 KHz RX Data Interrupt
1.2 MHz Tx Data Serial Clock
D8-D23
A0-A2,A13-A15,RD*,WR*
SCKR
RFS
TFS
SCKT
RXD
TXD
ADSIC
U406
GCB0-GCB3
To
Audio PA
U718
SDO
SC0
SC1
SC2
SCK
SRD
STD
SSI
SERIAL
DSP56001
U405
IRQB
IRQB
8KHz
SBI
DIN
DIN-
IDC
ODC
Data In
Data In*
SBI
To/From
ABACUS II
MAEPF-26001-O
Figure 9 DSP RSSI Port - RX Mode