NEC Property Management System Communication Interface Specification

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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 communicate using either an asynchronous or 
bisynchronous (BSC) method over a serial line. The transmission protocols are 
thoroughly described in the Architecture section. The descriptions of the messages 
transmitted are in the Descriptions section. The formats of the messages are in the 
Formats section. For a complete list of all messages, please see Appendix C, 
“Feature Codes” and Appendix D, “Function Codes”.
Information specified in the NEAX2400 IMS Hotel System PMS Interface 
Specifications document, but not included in this document are the messages 
specific to Model 120. Those messages are 56-3, 61-2, 58-1, 58-2, 58-3, 58-4 and 
58-5. These messages are for the Directory Assistance Interface [D-88] feature, 
which is not used in the United States. 
						

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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 
Waiting Lamp control, have less severe real-time requirements than 
interactive messages. Line 1 is only utilized for these messages and they will 
never be sent over Line 2 or Line 3.
Interactive messages are the Direct Data Entry messages and Maid Status 
Answerback messages. These messages require real-time interaction 
between the PMS and the NEAX and can therefore be isolated from the 
Hotel Processing messages. If Line 2 is installed, these messages will be 
transmitted over that line. If Line 2 and Line 3 are installed, these messages 
will load share over both lines. If only Line 1 is installed, these messages 
will be transmitted over Line 1.
The use of Line 1 is mandatory. If only Line 1 is installed, all messages are 
transmitted over it. Also, if Model 60 is being used, only Line 1 is necessary, 
as all of the Interactive messages are exclusive to Model 90.
It is very rare for Line 2 or Line 3 to be required. They are only needed if the 
traffic between the PMS and the NEAX is to be exceptionally heavy. And 
even the heavy traffic should only require Line 2.
The PMS may communicate with the NEAX through either an 
asynchronous transmission protocol or a bisynchronous transmission (BSC) 
protocol. 
						

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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 Contents ASCII (7bits)
Error Control Method VRC: Parity, LRC: BCC
Bit Transmission Order Priority is given to low order bits.
Transmission Intervals At each data generation. When a stream of information is 
transmitted to the NEAX continuously, an interval of 0.5 
seconds or more should be given between messages. Each 
message must be delimited by the EOT code.
Priority Sequence Primary office: NEAX
Secondary Office: PMS
Stop bit 1 bit or 2 bits
Error Control VRC: Even, odd or no parity.
LRC: (BCC) Exclusive OR of the message text, starting after the 
STX, and ending with (and including) the ETX.
Message  Composition One message constitutes one record; SOH, TTB and ETB are not 
used.
Message  Length Variable length, maximum of 128 characters (including STX and 
ETX).
Electrical Interface EIA RS-232C electrical standard interface
Signal Form EIA RS-404
Interface Distance Maximum of 50 feet between the NEAX and the PMS when not 
using a modem.
Word Framing 10 bits (1 start, 7 data, 1 parity, 1 stop) or 11 bits (1 start, 7 data, 
1 parity, 2 stop) 
						

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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 CodeHexadecimal 
Va l u eFunction
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 acknowledgment of an information 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
SAUAENQ 
						

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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 byte - ‘L’ [4CH].)
FTC -- Feature Code. (See below.) A list is provided in Appendix C, “Feature 
Codes”.
MSC -- Message Counter. This represents the length of the message. The count 
of characters starts at the FTC field and ends at the last character of the body of 
the message, not including the ETX. If the ETX character does not immediately 
follow the character specified by the message counter, an invalid message is 
assumed.
FC -- Function Code. This specifies the individual operation and processing for 
the feature designated by the Feature Code (FTC). A list is provided in 
Appendix D, “Function Codes”.
ETX -- End of text block. (One byte - 03H.)
BCC -- Block Check Code. 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.)
Feature Codes range in value from 00 to FF (hex). These codes define the “Major 
Category Codes” for service features.
Codes from 80 to FF are used as “Violation Codes”. When a specific message 
received from the PMS cannot be processed for some reason, 80 (hex) is added to 
the received Feature Code so that it will be handled as a Violation Code. If the 
NEAX regards a text as a Violation Code, the system data of the NEAX may be 
assigned so that a text of this type is returned to the PMS. Therefore, when the PMS 
has received a Violation Code, provisions should be made for the PMS to print out 
this violation.
Block Check Code Range 02H‘1’03H xx ‘!’
...
01234 6 89
STX SA UA EI FTC MSC FC MessageETX BCC
Message Count Range ‘L’ 
						

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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. 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 Figure 2-1). 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 
						

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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; quit on 4th Reject.
4 - Retry is 32 times; quit on 33rd No Answer.
5 - Retry is 3 times; quit on 4th Pause. 
						

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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 is 3 times; quit on 4th Reject.
4 - Retry is 32 times; quit on 33rd No Answer.
receive message from NEAX. 
						

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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 transmission 
of a message text or query, a query is sent up to 32 times.
Receiver Timer
Upon transmission of a positive acknowledgment for a start sequence or a message 
text, this timer begins counting and stops counting upon receiving a message text 
or an end code. This timer is set to 35 seconds. If a timeout occurs, the sender loses 
send rights.
Cabling 
ConsiderationsWhen the PMS is connected to the NEAX through a modem, the cables should just 
be “straight through” cables. There should be no crossing.
When the PMS is directly connected to the NEAX, use the following pin 
assignments:
Figure 2-4   Direct Connection Pin Assignments
Bisynchronous (BSC) Transmission
Line Control 
CharacteristicsThe characteristics of the signals transmitted across the communications link are as 
follows:
1FG
SD
RD
RS
CS
DR
SG
CD
ER 2
3
4
5
6
7
8
20FG
SD
RD
RS
CS
DR
SG
CD
ER1
2
3
4
5
6
7
8
20
Pin No. Signal CableSignal Pin No. NEAX PMS