NEC NDA-30115-001 User Manual
NDA-30115 Revision 1.0
Page 7
Property Management System - Communication Interface
Architecture
A Violation Code message will be sent to the PMS in the following cases:
•
When the message counter does not match the number of characters received.
•
When a station number not existing in the NEAX is specified in the message
data from the PMS.
data from the PMS.
•
Upon receipt of an invalid Wake Up time (e.g. 25:00).
Transmission
Sequence
Sequence
The sequence of transmitting a message is slightly different for the PMS and
NEAX. However, both sequences follow the same outline.
NEAX. However, both sequences follow the same outline.
The party which desires to send must first bid for sender rights. This is done by
sending the start sequence (see
sending the start sequence (see
). Once the start sequence has been sent
and acknowledged, that party is now the “sender” and the other party is the
“receiver”. (Unless both parties have simultaneously sent a start sequence. If this
occurs, the PMS must relinquish sending rights to the NEAX.) The receiver must
then respond with an answer control code (ACK, NAK, DLE <, DLE :, DLE ?)
before the Sender Timer (see
“receiver”. (Unless both parties have simultaneously sent a start sequence. If this
occurs, the PMS must relinquish sending rights to the NEAX.) The receiver must
then respond with an answer control code (ACK, NAK, DLE <, DLE :, DLE ?)
before the Sender Timer (see
) expires.
If no answer control code is received, the sender will resend the start sequence and
again wait for an answer control code.
again wait for an answer control code.
When an answer control code is received, the sender must respond before the
Receiver Timer (see
Receiver Timer (see
) expires. If the answer control
code is an ACK, the sender must send the message. Again, the receiver must
respond with an answer control code before the Sender Timer expires.
respond with an answer control code before the Sender Timer expires.
To finish the transmission sequence (regardless of its success), the sender must
send an End Code (EOT) to release sending rights. Once that is done, both parties
may begin the process over again by bidding for the sender rights.
send an End Code (EOT) to release sending rights. Once that is done, both parties
may begin the process over again by bidding for the sender rights.
In the transmission sequence figures that follow, these message names are used:
Table 2-4 Message Names
Name
Control Code
Explanation
Start Sequence
SA, UA, ENQ
Bid for sender rights
Message
STX, ..., ETX, BCC
Actual message sent
Query
ENQ
Query for expected answer control code
End Code
EOT
Release sender rights
Accept
ACK
Positive acknowledgment
Reject
NAK
Negative acknowledgment
No Answer
<Nothing>
Timer expired before an answer control
code was received
code was received
Contention
Start Sequence
Simultaneous start sequences
Interrupt
DLE <
Request to release sender rights
Abort
DLE :
Demand to release sender rights
Pause
DLE ?
Receiver’s queue full; please wait