NEC Property Management System Communication Interface Specification

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Table 2-5  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 Synchronous
Data Rate 4800 or 9600 bits/second (bps)
Frame Contents EBCDIC
Error Control Method CRC-16 (X
16 + X15 + X2 + 1)
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
Transfer Mode Non-transparent mode
Message Composition One message constitutes one record; SOH, ITB and ETB 
are not used. Only the non-transparent mode is used.
Message Length Variable length, maximum of 128 characters (including 
STX and ETX).
Electrical Interface RS-232C electrical standard interface
Signal Form RS-404
Interface Distance 50 feet
Word Framing 10 bits or 11 bits 
						

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The control codes used for the message texts are:
Table 2-6  Control Codes
Control CodeHexadecimal 
Va l u eFunction
SYN 32 Synchronization code.
STX 02 Indicates the start of a block.
ETX 03 Indicates the end of a block.
ENQ 2D Used as the start sequence code. It indicates a reception 
request to the other side and a request to answer an infor-
mation block just sent.
EOT 04 Indicates the end of transmission of a block or release of 
the data link by the sender.
ACK0 10, 70 Used alternately, these indicate the positive acknowledg-
ment of an information block or a start sequence.
ACK1 10, 61
NAK 3D Indicates the negative acknowledgment of an informa-
tion block or a start sequence.
WACK 10, 6B Used as the positive acknowledgment of an information 
block or start sequence and indicates that the receiver 
temporarily cannot receive data from the sender.
TTD 02, 2D Indicates that the sender cannot transmit the next infor-
mation block after the receipt of the answer to the previ-
ous information block sent from the receiver.
RVI 10, 7C Indicates the positive acknowledgment of an information 
block and asks the sender for sending rights.
PAD-L 55 Indicates the absolute beginning of the entire informa-
tion block.
PAD-T FF Indicates the absolute ending of the entire information 
block. 
						

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Transmission 
ProtocolThe messages sent between the NEAX and the PMS must have header and trailing 
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.)
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:
Figure 2-6   Message Data Format
Cyclic Redundancy Check Area 02H 03H xx
STX DataETX CRC PAD-T
FFH32H 55H 32H32H
PAD-LSYN SYN SYN
02H‘1’03H ‘!’...
STX SA UA EI FTC MSC FC MessageETX
Message Count Range ‘L’ 
						

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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 
them 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.)
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.
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). 
						

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Transmission 
Sequence
Table 2-7  Data Transmission Sequence (1 of 2)
Status ENQ STXETX,
CRCACK0/
ACK1NAK
Neutral (A) a: ACK0 -> 
(B)
b: NAK -> 
(A)
c: ENQ -> 
(D)
Waiting for 
STX (B)(ACK last 
received) -> 
(B)-> (C)
Waiting for 
ETX, CRC 
(C)f: NAK -> 
(B)
g: EOT -> 
(A)h: ACK0/1
i: NAK
c: RVI
j: EOT
-> (A)
Waiting for 
ACK after 
start 
sequence 
(D)f: ENQ -> 
(D)
g: EOT -> 
(A)d: ENQ -> 
(D)
e: EOT -> 
(A)d: ENQ -> 
(D)
e: EOT -> 
(A)Message -> 
(E)
j: EOT -> 
(A)f: ENQ -> 
(D)
g: EOT -> 
(A)
Waiting for 
ACK after 
message (E)d: ENQ -> 
(D)
e: EOT -> 
(A)d: ENQ -> 
(D)
e: EOT -> 
(A)d: ENQ -> 
(D)
e: EOT -> 
(A)k: Message 
-> (E)
l: EOT -> 
(A)m: Mes-
sage -> (E)
j: EOT -> 
(A) 
						

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Notes:
a: Preparation for reception complete.
b: Reception impossible.
c: Requests for preparation for reception (the PMS should not request this).
d: Transmitted up to 21 times.
e: Aborted at 22nd time.
f: Transmitted up to 7 times.
g: Aborted on the 8th time.
h: Message is received normally and preparation for next reception is complete.
i: Error found in message.
j: Interruption.
k: Information to be transmitted is present.
l: Information to be transmitted is absent.
m: Retransmission of message.
Table 2-8  Data Transmission Sequence (2 of 2)
Status EOT TTD WACK (Timeouts)(Transmis-
sion Request)
Neutral (A)ENQ -> (D)
Waiting for 
STX (B) -> (A) d: NAK -> 
(B)
e: EOT -> 
(A)
EOT -> (A)
(25 sec)
Waiting for 
ETX, CRC 
(C) -> (A)EOT -> (A)
(25 sec)
Waiting for 
ACK after 
start 
sequence 
(D) -> (A) d: ENQ -> 
(D)
e: EOT -> 
(A)d: ENQ -> 
(D)
e: EOT -> 
(A)f: ENQ -> 
(D)
g: EOT -> 
(A)
Waiting for 
ACK after 
message (E) -> (A) d: ENQ -> 
(D)
e: EOT -> 
(A)d: ENQ -> 
(D)
e: EOT -> 
(A)f: ENQ -> 
(D)
g: EOT -> 
(A)
(3 sec) 
						

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Timers and 
CountersRetransmission Counts
Timer Values
Table 2-9  Retransmission Counts
Meaning Count
The number of retransmissions of the start sequence when there is no 
answer after transmitting the start sequence.7
The number of retransmissions of the start sequence when NAK is 
received after transmitting the start sequence.7
The number of transmitting ENQs when WACK is received after the 
transmission of an information block15
The number of transmitting ENQs when there is no answer after the 
transmission of an information block. (3 second intervals)7
Table 2-10  Timer Values
Party Starting ConditionTimer value
(seconds)
NEAX Waiting for a start sequence answer. 1
Waiting for STX after transmitting the start sequence ACK. 20
Waiting for data reception complete (waiting for ETX, CRC). 20
Waiting for an answer after the transmission of a message. 1
PMS Waiting for a start sequence answer. 3
Waiting for STX after transmitting the start sequence ACK. 25
Waiting for data reception complete (waiting for ETX, CRC). 25
Waiting for an answer after the transmission of a message. 3 
						

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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 2-7   Direct Connection Pin Assignments
1FG
SD
RD
RS
CS
DR
SG
CD
ST
2
RT
ER
ST
1
2
3
4
5
6
7
8
15
17
20
24FG
SD
RD
RS
CS
DR
SG
CD
ST
2
RT
ER
ST
1
1
2
3
4
5
6
7
8
15
17
20
24
Pin No. Signal CableSignal Pin No. NEAX PMS 
						

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Property Management System - Communication Interface Message Descriptions
Chapter 3 Message Descriptions
There are several message groups:
Data Link Maintenance Messages
Maid Status
Message Waiting Lamp Control
Restriction Control
Check In/Check Out (Model 60)
Check In/Check Out (Model 90)
Wake Up/Group Announcement
Room Move/Swap/Copy (Model 60)
Room Data Change
Extension Report
Room Recovery (Model 60)
Room Recovery (Model 90)
Direct Data Entry (Model 90)
Extension Connection
Each message group will be described briefly in the following sections.
The NEAX equates rooms with extensions, one extension per room. The exception 
to this is the suite room feature. When this feature is activated in the NEAX, a 
primary extension represents a group of extensions in one or more rooms. For a 
suite room, the PMS should reference only the primary extension in its messages 
to the NEAX. All associated extensions will inherit the attributes of the primary 
extension and should effectively be ignored by the PMS.
Data Link Maintenance
These are the messages used by the PMS and NEAX to maintain communication.
The PMS must regularly send Nop Test messages with an interval of no more than 
60 seconds, and no less than 500 milliseconds, between each message. The NEAX 
will immediately respond with either a Nop Test Normal Answer, under normal 
conditions, or a Nop Test Recover Answer, if a database recovery for the NEAX is 
needed.
Nop Test Normal Answer -- Whenever a Nop Test message is sent by the PMS, 
the NEAX responds by sending this message, unless the NEAX has just 
finished an error recovery.
Nop Test Recover Answer -- If the NEAX has been performing an error 
recovery, this message is sent in response to the Nop Test in the place of the Nop 
Test Normal Answer message. 
						

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Recovery Start Report -- After receiving the Nop Test Recover Answer 
message, the PMS must download NEAX database information (see “Room 
Recovery (Model 60)” on page 27 and “Room Recovery (Model 90)” on page 
28). This message notifies the NEAX of the incoming download.
Recovery End Report -- Reports to the NEAX that the PMS database download 
is complete.
Data Link Release Request -- Used by either system to request a temporary 
release of the data link.
Data Link Release Confirmation -- Reply to the above message to acknowledge 
data link release request.
Extension Number Request -- Used by the PMS to request the current status of 
extension numbers.
Nop Test -- Under the standard protocol the PMS must send this message at 
least every 60 seconds, but not less than 500 milliseconds, to demonstrate that 
communication has been maintained.
Data Link FailureEither system may recognize a loss of communication by one or more of the 
following events:
Lack of system traffic for a 60 second interval: the Nop Test message from the 
PMS and the Nop Test Answer message (either Normal or Recover) from the 
NEAX insure that at least one message should be received less than every 60 
seconds.
Detection of hardware problems within the physical data. Note that the NEAX 
will put EIA pin number 6 (Data Set Ready) into the off state, indicating data 
set not ready, when the data link has been effectively turned off in the NEAX, 
either for maintenance or because of repeated, excessive errors.
Excessive protocol errors (NAK’ed transmission, ENQ’s with no ACK/NAK 
response).
Other conditions, such as unavailability of buffers or queuing capability, which 
result in an implied status change message which cannot be communicated to 
the other system.
Release of the data link requested and confirmed.
A data link failure will necessitate a database room exchange recovery procedure 
only if any implied status change cannot be communicated to the other system and 
cannot be queued for later transmission. If no messages have been lost, and can 
instead be retransmitted, no database recovery is necessary.