Digital (Astro) Mode Of Operation; Controller Section Circuitry - Motorola ASTRO Digital XTL 5000 Detailed Service Manual

Product Overview: Controller Section
2.7.2

Digital (ASTRO) Mode of Operation

In the ASTRO mode (digital mode) of operation, the transmitted or received signal is limited to a
discrete set of deviation levels, instead of continuously varying. The receiver handles an ASTRO-
mode signal identically to an analog-mode signal up to the point where the DSP decodes the
received data. In the ASTRO receive mode, the DSP uses a specifically defined algorithm to recover
information. In the ASTRO transmit mode, microphone audio is processed identically to an analog
mode with the exception of the algorithm the DSP uses to encode the information. This algorithm will
result in deviation levels that are limited to discrete levels.
2.7.3

Controller Section Circuitry

The controller section consists of the following:
• Voltage regulators
• Data connectivity circuitry (RS-232, USB, and SB9600)
• Daughtercard module, which contains the:
- Patriot microprocessor IC
- 64-Mbit (8MB) FLASH IC
- 8-Mbit (1MB) SRAM IC
• Modulation D/A conversion circuitry
• CODEC audio circuitry
• TX power-control circuitry
• Emergency circuitry
• V.I.P input/output paths
• Secure interconnect board interface
• Front connector interface for control heads and remote-mount interconnect boards (I.B)
• Rear connector for additional accessories
• DC power-in plug
The controller section controls receive/transmit frequencies, the display, and various radio functions
using either direct logic control or serial communication to external devices. The connector J0701
provides interface between the encryption module and the controller for encrypting voice messages.
Connector J0402 provides the accessory interface to the outside rear connector while connector
J0401 provides the control-head interface.
The controller section executes a stored program located in the FLASH ROM. Data is transferred to
and from memory via an RS-232 interface on the microprocessor. The memory location from which
data is read, or to which data is written, is selected by the address lines. Besides the host and DSP
code, the customer-specific programming features (codeplug) and tuning parameters also are stored
in the FLASH ROM. The SRAM is used as scratchpad memory for the microprocessor.
The controller section is powered by SW_B+ coming from the control head, which is regulated down
to a 5 V supply. This supply powers the entire controller section and its regulators. The SW_B+
supply is removed from the board when the radio is turned off by the control-head switch.
The microprocessor is powered by a 1.55-V regulator for the microprocessor core and a 2.85-V
regulator for the I/O and control lines, while the memory is powered by a 1.85-V regulator. The 2.85-
V regulator also supplies almost all of the discrete controller circuitry. These three regulators are all
supplied by a switched 5-V regulator, which also provides power for the SB9600 data bus and for
interface to certain legacy data and control signals.
6881096C74-B
2-13
May 25, 2005