NEC NDA-30115-001 manual Transmission, Protocol

Property Management System - Communication InterfaceArchitecture

Transmission	The messages sent between the NEAX and the PMS must have header and trailing
Protocol	sections as defined in the following format:

55H 32H 32H 32H 02H

03H xx FFH

PAD-LSYN SYN SYN STX Data ETX CRC PAD-T

Cyclic Redundancy Check Area

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.)

•STX -- Start of text block. (One byte - 02H.)

•Data -- The message data is describe below in Figure 2-6.

•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.)

•PAD-T -- The trailing pad character. (One byte - FFH.)

The message data is defined as follow:

02H ‘1’ ‘!’ ‘L’

STX SA UA EI

...

FTC MSC FC Message

Message Count Range

03H

ETX

Figure 2-6 Message Data Format

NDA-30115 Revision 1.0 Page 13