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 receive r to receive the data. Every transmi ssion 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
Valu e 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 ackno wledgment of an i nformation 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