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NDA-30115 Revision 1.0 Page 5
Property Management System - Communication Interface Architecture
The control codes used for the message texts are:
Transmission
Protocol
Before a message can be sent, a start sequence (also called a selecting sequence)
must be sent to urge the receiver to receive the data. Every transmission sequence
will begin with the sender sending a start sequence.
The start sequence is a three byte sequence:
Figure 2-1 Start Sequence
Table 2-2 Control Codes
Control Code
Hexadecimal
Value
Function
STX 02 Indicates the start of a block.
ETX 03 Indicates the end of a block.
EOT 04 Indicates the end of transmission of a block or release of the
data link by the sender.
ENQ 05 Used to query other party for expected response.
ACK 06 Indicates the positive acknowledgment of an information block
or start sequence.
NAK 15 Indicates the negative acknowledgment of an information
block or start sequence.
DLE < 10, 3C Indicates the receiver interrupting to ask for sending rights.
DLE : 10, 7C Indicates the receiver interrupting to ask the sender to stop
transmission and to release the data link.
DLE ? 10, 3F Used as the negative acknowledgment of block and indicates
that the receiver temporarily cannot receive data from the
sender.
05H
‘1’
‘!’
012
SA
UA
ENQ