Tait T2000-A76 Operation Manual - Commands to The Remote Radio
March 2003
M2303-00-P00-805
17
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Commands to the Remote Radio
Commands to the remote radio are sent using the SEND_SDM CCDI command. It has the format :
s [LEAD_IN_DELAY] [DATA_MESSAGE_ID] [COMMAND] [DATA]
Notes: The [DATA] field is only sent with some commands.
The [COMMAND] and [DATA] fields are limited to a combined length of 32 hex characters.
The SEND_SDM is sent by the central control AVL application to the despatcher radio, then, after the specified
SDM Lead In Delay, over-air to the remote AVL radio.
‘ s ‘
‘ s ‘ is sent as a single ASCII hex character and represents the SEND_SDM command.
[LEAD_IN_DELAY]
The SDM Lead In Delay is two ASCII hex characters representing the delay between radio transmitter key-up
and the start of data transmission. The range that can be entered is 00 to FF.
The Lead In Delay is calculated by multiplying the number by 20 ms. A minimum of at least 100 ms of Lead In
Delay is required, so 00 to 04 will always be treated as 05. This corresponds to a Lead In Delay between 100
ms and 5.1 seconds, in steps of 20 ms. Refer to the
Polling the Remote AVL radio
section.
[DATA_MESSAGE_ID]
The [DATA_MESSAGE_ID] is an 8-character string representing the SDM Data ID of the radio to which the
SDM is sent. It can be any alphanumeric characters. “
*
“ is the wildcard for any character. e.g. 12
**
5678
The first four bytes are generally the fleet ID, the second four the radio ID.
When a radio receives a SDM message, the Data ID is checked against the ID entered in the radio
configuration database. If the Data ID matches, the radio sends a response to indicate this.
If the Data ID does not match then the SDM data is ignored.
[COMMAND]
The [COMMAND] part of the SEND_SDM contains the SDM text with commands to the remote radio.
The table below shows the structure of the [COMMAND] byte.
Bit
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Function
0
Command Type
Return
Address
Parameter