E.F. Johnson Company 5100 Series, Руководство по обслуживанию

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CIRCUIT DESCRIPTION
5-18
Q501. Transistor Q501 responds to the base drive level
by varying the DC control voltages applied to pin 2 of
the RF PA which controls the RIF power level of
module U502. The ALC IC also controls the base
switching to transistor Q502 via pin 12, BIAS.
The D/A IC (U503) controls the DC switching of
the transceiver board. Its outputs, SC1 and SC3 (pins
12 and 14, respectively), control transistor Q503
which then supplies Tx 5V and Rx 5V to the trans-
ceiver board. The D/A also supplies DC bias to the
detector diode (CR501) via pin 7, and the REF V
signal to the ALC IC (U504).
5.8 USER INTERFACE BOARD (ALL)
NOTE: The following describes all three logic
versions described in Section 1.13.
5.8.1 INTRODUCTION
The User Interface Board contains the main
microcontroller which controls all functions of the
transceiver. In addition, it contains memory (Flash,
SRAM, and EEPROM), A-D and D-A converters, the
interface to the graphic display, audio circuitry, and
various other interfaces.
5.8.2 MICROCONTROLLER (U2)
Microcontroller U2 is PowerPC
®
based which
gives this transceiver processing power equal to some
current desktop computers. This microcontroller
provides all transceiver control functions except signal
processing which is provided by the DSP U1 on the
logic board.
Functions provided by U2 include detecting key
and button presses, processing incoming and outgoing
calls, displaying operational data to the user, and coor-
dinating control of the other processor (DSP) located
on the logic board. Communication with the DSP is
via a 16-bit host port.
The operating speed of U2 is controlled by
4.9152 MHz crystal Y1. The internal clock is five
times this frequency or 24.575 MHz (25 MHz
operational).
5.8.3 MEMORY
Early Units (Versions A and B in Section 1.13)
Memory devices include Flash, SRAM,
EEPROM, and DSP SRAM. There is 4 megabyte of
Flash that is used primarily for code storage but can
can also be used for as non-volatile memory.
The SRAM (static RAM) consists of one 256K x
16 and one 512K x 16 device (U2 and U3), each of
which used a different chip select. A 32K x 8
EEPROM (U16) is used to store personality data.
Later Units (Version C in Section 1.13)
Memory devices include Flash, SRAM,
EEPROM, and DSP SRAM. There is 8 megabyte of
Flash that is used primarily for code storage but can
can also be used for as non-volatile memory.
The SRAM (static RAM) consists of a 1M x 16
device (U6). A 32K x 8 EEPROM (U16) is used to
store personality data.
5.8.4 GRAPHICAL DISPLAY
The graphical display is connected to J4. This
type of display allows text and icons to be positioned
anywhere on the display and allows text to be
displayed in various fonts (type styles).
5.9 LOGIC BOARD (VERSION C)
NOTE: The following describes the Version C logic
board described in Section 1.13.
5.9.1 INTRODUCTION
The Digital Signal Processing (DSP) functions
are performed by the DSP chip (U15) and the CODEC
(U27) with the support of microcontroller U1 on the
UI board. Functions previously performed in hardware
like filtering and limiting are performed by software
running in the DSP chip.
UI BOARD (ALL VERSIONS)