Icom IC-751A Service Manual page 32

4-5-5 MATRIX UNIT
The MATRIX UNIT consists of a matrix board, matrix switch
board, and mode switch board. It processes the front panel
matrix input and transmit and receive data.
MATRIX TABLE
Custom IC
RP5G01 007
YO ¥1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Y9
TEN NC BAND MODE R SCAN
KEY FU BAN REMOTE| RIT
SEARCH| Rp rtecock] [CLOCK
DBO
PITCH | REMOTE] [YF
CLEAR k_ WP
DBI
MSE
IN
Ne NS
DB2
RIT af
SPLIT
CLEAR CW (DUPLEX)
. IN Nn N N
DIAL
DB3
SCAN VFO VFO PITCH
START A/B A=B RTT
Distr [A [KS N Ne
DB4
MEMORY| N-SSB
Na NS N AE
HAM/ALL | MWi DBS
DISP.
(GENE) EMO) RSW
DB6
RIT/ATX | MW2 Soar
ON/OFF (MEMO SEND KO Xr KIN
DB7
Fig. 18
(1) YO—-DBO-DB3 (TEN KEY)
Following is a matrix for frequency settings and band
changing through the use of an external RC-10 ten key unit
(optional).
0
0
0
0
0
0
0
1
1
1
1
1
(2) YO—-DB4 (SCAN START/STOP)
This matrix starts and stops the scan. It is controlled by the
[SCAN] SWITCH and also by the [SQUELCH] CONTROL
and the DIAL LOCK SWITCH through IG2(b) and Q3. When
the [SCAN] SWITCH is pushed, one pulse signal is input to
this matrix to repeatedly start and stop the scan operation.
Three types of scanning operations (MEMORY SCAN,
PROGRAMMED SCAN, and SELECTED MODE SCAN) are
available. During VFO operation, PROGRAMMED SCAN is
automatically selected; during the memory channel
operation, MEMORY SCAN is selected. R14 on the LOGIC
UNIT adjusts the scanning speed. S10 reactivates the scan if
it is interrupted when the squelch is open.
(3) Y1—DB4 (VFO A/B)
This matrix selects VFO A or VFO B via the [VFO] SWITCH.
When VFO B is selected, pin 20 of the CPU becomes HIGH.
Operation mode, frequency, and ham/general selections are
stored independently in each mode.
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