Message Structure; Command Message Structure (Cdm-600L To Buc) - Comtech EF Data CDM-600L Installation And Operation Manual

CDM-600L Satellite Modem
BUC FSK Communications
Note: If the BUC does not respond within the maximum response time the IDU should
cyclically repeat the command.
On power-up, the Tx carrier is Off until the BUC is commanded to turn the carrier on
(unless the unit is commanded into the power On mode at the factory). The BUC does not
allow the carrier to be turned On unless the PLL is locked, and automatically turns the
carrier Off in the event the PLL goes out-of-lock. If the PLL then comes back into lock,
the BUC restores the carrier to the most recent requested state by the IDU. The carrier
enable/disable function is implemented by switching On/Off the switched regulators of the
BUC amplifier chains (a "sleep mode").
The BUC is equipped with a calibrated power sensor for measuring the power
delivered to the antenna for rated output to 20 dB backed off. This value, in dBm,
is available via the M&C for power level monitoring and AGC.
Refer to BUC manufacturer specifications for reported power accuracy.
16.1.1 Transmission Interface
Each transmitted data packet consists of 7 bytes of information. The BUC only
accepts a command if the first data byte contains the appropriate address.
Commands are only executed if the checksum coincides, but a status response is
sent if the address is correct and the command number is within the valid range.
16.2

Message Structure

16.2.1

Command Message Structure (CDM-600L to BUC)

Byte
1
2
3
4
5
6
7
Name
Address Address of BUC
Command Request Status
Tx On/Off
Change Address
Set Carrier Frequency
Data Byte 1 Not used if command:
Tx control if command:
New address if command:
Carrier Frequency if command:
Data Byte 2 Not used if command:
Not used if command:
Not used if command:
Carrier Frequency if command:
Data Byte 3 Not Used
Data Byte 4 Not Used
Checksum Algebraic sum of bytes 1 - 6
16–2
Description
= 0x01
= 0x02
= 0x03
= 0x04
= 0x01
= 0x02
= 0x03
= 0x04
Revision 0
MN/CDM600L.IOM
Value
0x01 to 0x0f
0x01
0x02
0x03
0x04
0xAA
0=Off, 1=On
0x01 to 0x0f
MSbyte
0XAA
0xAA
0xAA
LSbyte
0xAA
0xAA