Vocoder Section - Motorola ASTRO Digital Saber Service Manual

The controller performs the programming of all peripheral ICs. This is
done through a serial peripheral interface (SPI) bus. ICs programmed
through this bus include the synthesizer, DAIC, reference oscillator,
display, and ADSIC. On secure-equipped model, the encryption board
is also controlled through the SPI bus.
In addition to the SPI bus, the controller also maintains two
asynchronous serial busses; the SB9600 bus and an RS232 serial bus.
The SB9600 bus is for interfacing the controller section to different
hardware option boards, some of which may be external to the radio.
The RS232 is used for the function of a common data interface for
external devices.
User input is handled by the controller through top rotary controls
and side buttons. On models with a display, an additional 3 x 2 or 3 x
6 keypad are also read. User feedback is provided by a single bicolor
LED on the top and a two-line, fourteen-character display if equipped.
The controller schedules the activities of the DSP through the host
port interface. This includes setting the operational modes and
parameters of the DSP. The controlling of the DSP is analogous to
programming analog signaling ICs on standard analog radios.

Vocoder Section

Refer to Figure 5 and your specific schematic diagram.
The vocoder section of the VOCON board is made up of a digital signal
processor (DSP-U405), 24k x24 static-RAM (SRAMs-U414, U403, and
U402), 256kB FLASH ROM (U404), ABACUS/DSP support IC (ADSIC-
U406), and an audio PA (U401).
The FLASH ROM (U404) contains the program code executed by the
DSP. As with the FLASH ROM used in the controller section, the FLASH
ROM is reprogrammable so new features and algorithms can be
updated in the field as they become available. Depending on the mode
and operation of the DSP, corresponding program code is moved from
the FLASH ROM into the faster SRAM, where it is executed at full bus
rate.
The ADSIC (U406) is basically a support IC for the DSP. It provides
among other things, the interface from the digital world of the DSP to
the analog world. The ADSIC also provides some memory
management and provides interrupt control for the DSP processing
algorithms. The configuration programming of the ADSIC is
performed by the MCU. However some components of the ADSIC are
controlled through a parallel memory mapped register bank by the
DSP.
In the receive mode, The ADSIC (U406) acts as an interface to the
ABACUS IC, which can provide IF data samples directly to the DSP for
processing. Or the IF data can be filtered and discriminated by the
ADSIC and data provided to the DSP as raw discriminator sample data.
The latter mode, with the ADSIC performing the IF filtering and
discrimination, is the typical mode of operation.
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