Issue 1.00 DLA200 Dual Line Amplifier Units Page 7
Remote control interfacing
The DLA200 dual block control system unit may be monitored and controlled remotely either via a
RS232 or a RS485 multidrop bus. The connection is made via the 15 way D type on the rear of the unit
and configured as described earlier.
The unit transmits and receives data serially in an asynchronous format using the standard ASCII
character set. The serial data consists of message frames composed of the following message characters:
STX, BYTE COUNT, DEVICE ADDRESS, INSTRUCTION, BODY, CHECKSUM, ETX. All
characters are compulsory except for the message body. The presence of a message body is determined by
the message type (INSTRUCTION). The total number of message characters in a message frame may
range from a minimum of 6 to a maximum of 255.
The remote control follows the following protocol: (in byte form)
[STX] start of message character #02.
[B] char defining how many characters are in the message including the STX & ETX parts.
[A]
Address of unit
. Address ranges from ASCI character 32 to 47. (configurable via dip
switches - see earlier
[I]
Instruction number.
The possible instructions are:
STATUS REQUEST character 32
STATUS REPLY
character 33
CONFIGURE
character 34
[MESSAGE]
numerous characters from length 0 upwards. If no message present enter a 0.
[CHKSUM]
The checksum is used to verify the accuracy of the message frame. The checksum is defined as
the summation of all the bytes in the message,
beginning
with the 3rd byte (DEVICE
ADDRESS) and extending through the body of the message,
ending
with the last byte before the
checksum. The total of the bytes is then ANDed with 255 so that the checksum is truncated to a
single byte.
[ETX] End of transmission character #03
All message to and from the unit follow the above protocol with a character format of 8 data bits, one
stop bit, no parity, baud rate 300, 2400, 9600 or 19200. Note that all numeric values are shown as
decimal
.
Message Information
The message protocol for this unit has been made to emulate the RCU100 units therefore the bands are
set as ‘A’ and ‘B’ not ‘1’ and ‘2’ as the metalwork/front panel say.
Status Request message:
In order to find out the STATUS of the unit a status request message must be sent.
STATUS REQUEST:
Instruction 32
Example for a Status Request to a unit that has been configured as address 32. The following
characters should be sent.
