Yaesu FT-817 Technical Supplement page 13

Control Circuitry
Microprocessor Circuit
The microprocessor circuit, which is composed of CPU
IC Q4004 (HD6432345) and EEPROM IC Q4006
(AT24C64AN), performs various types of processing, such
as control signals, serial I/O, A/D conversion, dial counter
circuit control, key input, and display functions.
The EEPROM memorizes various parameters and settings
(transmission frequency range, transmission output con-
trol) and carrier points according to the transceiver ver-
sion and the contents of memory channels.
Reset Circuit
The reset circuit consists mainly of PANEL Unit ICs Q4014
(PST3445), Q4015, Q4016 (both 2SC4154), and Q4010,
Q4011 (both 2SA1602A), and associated capacitors and
resistors. This circuit controls the power-down input port,
CPU reset input, keyer CPU, and related circuits.
Dial Counter Circuit
The dial counter circuit consists of Main Dial and SEL (Se-
lector) Knob. This circuit detects a two-phase pulse hav-
ing a phase difference of 90 degrees and delivers it to CPU
IC Q4006.
Serial Data Communication Circuit
The Serial Data Communication Circuit consists of ICs
Q4008 (TC7SU04FU), Q4009 (TC74HC139AF) and tran-
sistor Q4010 (2SA1602A), etc. on the PANEL-Unit. These
ICs distribute a set of serial data (Data/Clock/Strobe) gen-
erated by CPU to various devices, such as CAR-DDS, REF-
DDS, E.VOL, D/A, or Shift-Register for controlling ana-
log switching , band switching, VCO selection, etc. Serial
data communication is clock synchronous for the above
purposes, whereas the serial data is transferred to an asyn-
chronous signal for the CAT system for external computer
control of the transceiver).
Various types of data, such as operating frequency, mode,
and display data, are processed by CPU IC Q4004
(HD6432345).
The CAT (external computer control) signals are converted
to RS232 interface standard levels by the optional CAT
Interface Cable (CT-62).
Circuit Description
Key Matrix Circuit
The key matrix circuit consists of PANEL Unit diodes
D4001-D4003 and D4008 (all IMN10) and the panel key
switches arranged on the matrix. When a key is pressed,
this circuit reads the input data for processing by the CPU.
Analog-Digital Converter Circuitry
Forward and reflected voltage, ALC, DISC, S-meter, etc.
metering options are selected by MAIN Unit IC Q1073
(BU4053BCF: Lot 1 - 76, CD4053BPWR: Lot 77 -) and
are fed to the A/D port of CPU IC Q4004 (HD6432345)
for conversion into digital values to be processed prior to
display on the LCD. The individual voltages, converted
into digital values, are displayed as PO, SWR, ALC, VCC,
and S-meter indications on the LCD panel.
LED Drive Circuit
The LED drive circuit consists of PANEL Unit transistors
Q4018 and Q4019 (both 2SC1623) and the LEDs. This cir-
cuitry drives (turns on/off) the appropriate LEDs.
LCD Circuit
Data processed by the CPU IC is sent as parallel data to
LCD Unit DS4001.
CTCSS Tone Generator Circuit
The CTCSS tone generator circuit consists mainly of CPU
IC Q4004 (HD6432345) and active filter IC Q1094
(NJM2902V).
Electronic Keyer Circuit
The electronic keyer circuit consists of CPU IC Q4004
(HD6432345). When the CW mode is selected, this cir-
cuit controls the generation of Morse characters.
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