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CAT System Computer Control
A value of 1011 1110 0110 1111 (the 2-s comple-
ment of the previous example) produces a minus off-
set of -9989.375 Hz. See the byte chart below for a
breakdown of the conversion process.
Clarifier Offset Data Bytes (5-6)
Byte 5
1* 0
1
1
1
1
1
1* (" – " flag) 011 1110 0110 1111 =
(–) 3E6F (HEX) = (–) 15,983
(–) 15,983 x 0.625 = (–) 9989.375 Hz
*Note - Remember that the first bit is a flag: "0" for
positive offsets, "1" for negative offsets, and is not
included in calculations.
Operating Mode - The operating mode is ex-
pressed as a three-bit binary code in offsets 5 ~ 7. Bit
0 contains a User Mode flag, while Bits 1~4 contain
"dummy" values (unused).
Operating Mode Byte (7)
Bit 0*
Bit 1
Bit 2
Bit 3
User
N/A - "dummy bytes
Mode
0
X
X
X
0XXXX010 = CW operation, User Mode Off
Bits 1 ~ 3 are "dummy bits" -
0 = off
any 1/0 combination may ap-
1 = on
pear in here, but is insignificant.
Page 92
16-B
D
YTE
ATA
Byte 6
0
0
1
1
0
1
1
1
Bit 4
Bit 5
Bit 6
Bit 7
Mode Data
(3-bit Code)
X
0
1
LSB
000
USB
001
CW
010
AM
011
FM
100
RTTY 101
PKT
110
R
S
ECORD
TRUCTURE
IF Filter Selection - The first data bit (Bit 0) con-
tains a flag indicating normal or alternate reception
mode (see table). The remainder of the data byte con-
tains 2 x 4-bit fields separated by a dummy bit. The
first field holds the 3-bit binary code for the 8.2 MHz
2nd IF filter selection, while the second holds the 455
kHz 3rd IF selection. Codes are listed in the bottom of
1
the table below.
IF Filter Selection Byte (8)
Bit 0*
Bit 1 Bit 2
8.2 MHz 2nd IF
Thru
RX
2.4k
Mode
2.0k
500
250
Mode*
CW
0
USB
1
LSB
VFO/MEM Indicators - Five flags indicate the sta-
tus of Clarifier (Rx & Tx), Repeater Offset (+/-), and
Antenna Selection (A/B/RX). Bits 0 and 1 are not used
(dummy values).
0
Clarifier, RPT, ANT Status Byte (9)
Bit 0*
Bit 1
TX
RX
CLAR
CLAR
Note: for all flag bits, 1 = On, 0 = Off
for ANT SELECT:
00 = ANT-A, 01 = ANT-B, 10 = RX ANT
Bit 3
Bit 4 Bit 5 Bit 6
455 kHz 3rd IF
000
6.0k
001
X
2.4k
010
2.0k
011
500
100
250
AM
RTTY
ENV
LSB
SYNC
USB
Bit 2
Bit 3
Bit 4 Bit 5 Bit 6
ANT
+RPT
–RPT
SELECT
O
PERATING
Bit 7
000
001
010
011
100
PKT
LSB
FM
Bit 7
X
X
M
ANUAL
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