NEC Property Management System Communication Interface Specification

NDA-30115  Revision 1.0Page 1
Property Management System - Communication Interface Overview
Chapter 1 Overview
This document is a description of the interface between the NEC NEAX2400 IMS 
(hereafter referred to as the NEAX) and the hotel’s Property Management System 
(PMS). This document contains almost all (see below) of the information specified 
in the NEAX2400 IMS Hotel System PMS Interface Specifications (document ND-
90265 (E) Issue 2), and is intended to replace it.
The PMS and NEAX may...

Page 2NDA-30115  Revision 1.0
Overview Property Management System - Communication Interface
This Page Left Blank. 

NDA-30115   Revision 1.0Page 3
Property Management System - Communication Interface Architecture
Chapter 2 Architecture
The PMS communicates with the NEAX over one or more serial cables. A 
maximum of three lines can be provided as data links between the NEAX and the 
PMS.
The three lines are designated as Line 1, Line 2 and Line 3. Line 1 is used for 
Hotel Processing messages; Line 2 and Line 3 are used for Interactive 
messages.
Hotel Processing messages, such as Check In, Check Out and Message...

Page 4NDA-30115  Revision 1.0
Architecture Property Management System - Communication Interface
Asynchronous Transmission
Line Control 
CharacteristicsThe characteristics of the signals transmitted across the communications link are as 
follows:
Table 2-1  Line Control Characteristics
Item Conditions
Control Method Contention method (point to point)
Operating Mode Half duplex (if modems are used, set to full duplex)
Synchronization Start-stop system
Data Rate 1200, 2400 or 4800 bits/second (bps)
Frame...

NDA-30115   Revision 1.0Page 5
Property Management System - Communication Interface Architecture
The control codes used for the message texts are:  
Transmission 
ProtocolBefore 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 SequenceTable 2-2  Control Codes
Control...

Page 6NDA-30115  Revision 1.0
Architecture Property Management System - Communication Interface
The messages (but not the control codes or start sequence) sent between the NEAX 
and the PMS must have header and trailing sections as defined in the following 
format:
Table 2-3  Base Message Format
The message format breaks down as follows:
STX -- Start of text block. (One byte - 02H.)
SA -- System Address. (One byte - ‘1’ [31H].)
UA -- I/O Unit Address. (One byte - ‘!’ [21H].)
EI -- Entry Index. (One...

NDA-30115   Revision 1.0Page 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.
Upon receipt of an invalid Wake Up time (e.g. 25:00).
Transmission 
SequenceThe sequence of transmitting a message is slightly different for the PMS and 
NEAX....

Page 8NDA-30115  Revision 1.0
Architecture Property Management System - Communication Interface
From the NEAX to the PMS
Figure 2-2   NEAX to PMS Protocol
Start
SequenceAccept
Reject
No Answer
Contention
Interrupt
Abort
PauseMessageAccept
Reject
No Answer
Interrupt
Abort
Pause
End
Code
Wa i t
1 second
SendReceiveReceiveSendSend
retry quitretryretry
retry
retry quitquit
quit
quit
1
23
4
5
Query
1 - Retry is 3 times; quit on 4th Reject.
2 - Retry is 15 times; quit on 16th No Answer.
3 - Retry is 3 times;...

NDA-30115   Revision 1.0Page 9
Property Management System - Communication Interface Architecture
From the PMS to the NEAX
Figure 2-3   PMS to NEAX protocol
Start
SequenceAccept
Reject
Contention
Interrupt
PauseMessageAccept
Reject
No Answer
Interrupt
Pause
End
Code
Wa i t
1 second
SendReceiveReceiveSendSend
retry
quit
Query
Wa i t
1 second
No Answerquit
retry
continue
quit
1
23
4
1 - Do not respond. Immediately cease send attempt and
2 - Ignore Interrupt and send message if 8 messages in queue.
3 - Retry...

Page 10NDA-30115  Revision 1.0
Architecture Property Management System - Communication Interface
TimersThe following timers are used to maintain data transmission:
Sender Timer
Upon sending a start sequence, message text or query, this timer begins counting 
and stops counting upon receiving a valid answer control code. This timer is set to 
one (1) second. If a timeout occurs after the transmission of a start sequence, a start 
sequence will be resent up to 15 times. If a timeout occurs during the...