NEC NDA-30115-001 用户手册
NDA-30115 Revision 1.0
Page 13
Property Management System - Communication Interface
Architecture
Transmission
Protocol
Protocol
The messages sent between the NEAX and the PMS must have header and trailing
sections as defined in the following format:
sections as defined in the following format:
Figure 2-5 Base Message Format
The elements of the message is as follows:
•
PAD-L -- The leading pad character. (One byte - 55H.)
•
SYN -- Synchronization character. At least three of these should be transmitted.
(One byte each - 32H.)
(One byte each - 32H.)
•
STX -- Start of text block. (One byte - 02H.)
•
Data -- The message data is describe below in
•
ETX -- End of text block. (One byte - 03H.)
•
CRC-- Cyclic Redundancy Check. This is computed by an exclusive OR of the
message from the SA to the ETX (inclusive). Detection of an STX starts the
computation (but the STX is not included). Detection of an ETX stops the
computation (and the ETX is included). (One byte.)
message from the SA to the ETX (inclusive). Detection of an STX starts the
computation (but the STX is not included). Detection of an ETX stops the
computation (and the ETX is included). (One byte.)
•
PAD-T -- The trailing pad character. (One byte - FFH.)
The message data is defined as follow:
Figure 2-6 Message Data Format
Cyclic Redundancy Check Area
02H
03H xx
STX
Data
ETX CRC
PAD-T
FFH
32H
55H 32H
32H
PAD-LSYN SYN SYN
02H ‘1’
03H
‘!’
...
STX
SA
UA
EI
FTC
MSC
FC
Message
ETX
Message Count Range
‘L’