Remote Control; Serial Communications Rs232 / 485 - PEAK COMMUNICATIONS DBUH Series Installation And Operating Handbook

REMOTE CONTROL

Serial Communications RS232 / 485

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, UNIT 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 ASCII character 001 to 255. If in RS232 Mode
this address can be anything in the 001 to 255 range.
[I] Instruction number. See List below
[MESSAGE]
Numerous characters from length 0 upwards.
[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 19200, 9600, 4800, 2400, 1200 or 300. Note; that all
numeric values are shown as decimal.
Issue 3.20 DBUH / DLAH / DTLH Installation and Operation Handbook Page 14