Lucent Technologies DEFINITY Enterprise Communications Server And GuestWorks Property Management System Interface Specifications

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
29 Exchange Protocol and Message Responses 
The ACK and NAK control characters are transmitted back to the sender by the 
receiver to indicate positive or negative acknowledgment to the transmitted 
message, respectively. An ACK means that the message was received and the 
sender can continue with another message. A NAK means that the message was 
not received and that the message should be resent. The ENQ control character 
is transmitted by the sender when the ACK or NAK acknowledgment of a 
transmitted message is not received by the sender, and is a request for a repeat 
of the ACK or NAK response. An ENQ is NOT required before sending a message 
package from the PMS to the switch. A sample sequence is shown in Figure 10
.
Figure 10. Sample Acknowledgment Sequence
Exchange Protocol and Message 
Responses
For the following discussions, the definition of sender and receiver is relative to 
the origination of the message because of full duplex operations.
The parameters shown in Ta b l e 4
 are administerable. See “Administration 
Options” starting on page 3 for details. The acronyms shown in the table are used 
in this section when referring to the parameters.
Table 4. PMS Link Administration Parameters
Parameter Administrable Entry
PMS Link Maximum Retransmission 
Requests (MRR)1-5 retransmissions
PMS Link Maximum Retransmissions (MR) 1-5 retransmissions
Milliseconds before PMS Link
Acknowledgment Timeout (LAT)100-300 ms (N)
100-500 ms (T)
100-1500 ms (A)
(+125ms tolerance)
Seconds Before PMS Link Idle Timeout (LIT) 5-20 seconds 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
30 Exchange Protocol and Message Responses 
Sending Rules
The sender must adhere to the following rules:
1. The BCC must be calculated for characters following the STX, including 
the ETX, and transmitted as the terminating character of a message 
packet. If the BCC is incorrect, the receiver will respond with a NAK.
2. The entire message (STX to BCC) must be transmitted within 200 ms (N) 
or within 350ms (T) (A). If the message is not completely transmitted within 
this time, the receiver will respond with a NAK, ignore the rest of the mes-
sage (which is interpreted as characters received outside of the framework 
of a message), and log the errors.
3. The next message cannot be transmitted until the last message has been 
acknowledged as successfully transmitted or is flushed because of mes-
sage failure (administered MRR of unanswered ENQs and/or NAK retrans-
missions). If this rule is violated, the receiver may accept and process 
messages, but message overflow is likely (which possibly can result in link 
tear down).
4. If neither an ACK or a NAK is received from the receiver within the LAT, 
after transmission of the BCC, the sender will transmit an ENQ requesting 
a repeat from the receiver of that ACK/NAK response. After the initial LAT 
delay with no response from the receiver, the sender will issue up to 
MRR-1 subsequent ENQs in intervals of LAT (for a total of up to MRR 
ENQs requesting a message acknowledgment), after which the sender will 
flush the message. If the sender does not send an ENQ within the LAT, the 
receiver assumes that the ACK/NAK has been received. Consequently, if 
the sender transmits an ENQ after the LAT, the receiver logs the event as 
an unsolicited ENQ and sends a NAK.
5. The sender must assume that an expected ACK or NAK response to a sent 
message or an ENQ response to a received message does not occur in a 
message packet (STX through BCC) being simultaneously received. If the 
sender embeds an ACK or ENQ in a message, the receiver ignores the 
ACK or ENQ (and does not include in the BCC calculation), and logs an 
error
*. If the sender embeds a NAK in a message (that is, it is really not a 
nibble with value 0x15 but a message response), the receiver transmits a 
NAK and logs an error since the NAK is considered part of the message 
text which causes the BCCs to be different.
* Since the normal mode requires 0x0-to-0xa conversion in the message text, the ACK and ENQ char-
acters are not possible in the message text if the sender and receiver rules are followed. However, 
these values are possible in the transparent mode. The difference between interpreting these charac-
ters as control characters or message text is the presence of a DLE character before these charac-
ters. See the section “Timeout Control” starting on page 33
. 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
31 Exchange Protocol and Message Responses 
6. Upon receipt of a NAK from the receiver, the sender will retransmit the cur-
rent message using the same message count (up to MRR attempts - see 
next note); retransmission must be started within the LAT after receipt of 
the NAK. If the transmission is not started (or an ENQ received) within LAT, 
the switch will drop the link.
7. When MRR retransmission is made due to receiver NAKs, or MRR ENQs 
are sent to the receiver due to nonacknowledgement, the sender will flush 
the message and log the unsuccessful transmission. If the sender does not 
flush the message and keeps sending the message, the receiver treats the 
message as a new message.
8. Each time a new message is sent, the message count field must be incre-
mented by one, modulo (10) (N), or modulo (10) + 2 (T) (A).
9. The priority among conflicting actions at a sender is as follows:
a. Message currently being sent
b. Responses to ENQ
c. ACK or NAK to received message
d. Retransmission in response to NAK
e. Generic message.
Receiving Rules
The receiver must adhere to the following rules:
1. Verify that the entire message (STX through BCC) is received 
within 200 ms (N) or 350 ms (T) (A). Otherwise, corrupted messages could 
be processed.
2. Calculate a BCC for the received characters following the STX, including 
the ETX; compare the calculated BCC against the received BCC to insure 
message integrity. Otherwise, corrupted messages could be processed.
3. As soon as possible after the BCC verification (after 10 ms if receiver is not 
actively sending a message), the receiver must transmit a response. If the 
receiver waits longer than the LAT, the sender will send an ENQ.
4. The receiver must complete sending a message packet before transmitting 
an ACK or NAK response to a received message. If the receiver breaks 
this rule by embedding an ACK or ENQ in an outgoing message, the 
sender ignores the ACK (and does not include it in the BCC calculation), 
logs an error, and sends an ENQ after the LAT times out. If the receiver 
breaks this rule by embedding a NAK in an outgoing message (that is, it is 
not a nibble with value 0x15 but a message response), the sender trans-
mits a NAK in response to the outgoing message since the NAK is consid-
ered part of the message text which causes the BCCs to be different. Also, 
the sender logs an error and sends an ENQ after the LAT times out. 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
32 Exchange Protocol and Message Responses 
5. After transmitting the ACK/NAK response, the receiver must repeat the 
previous reply if an ENQ is received within the LAT after the original trans-
mission of the ACK/NAK; this may be repeated until the maximum MRR 
(for a total of MRR received ENQs at LAT intervals). If the receiver does not 
reply, the sender transmits another ENQ.
6. The receiver must respond with a NAK to a message transmission when 
the following occurs:
— A period of 200 ms (N) or 350ms (T) (A) has expired since reception 
of an STX with no BCC received (incomplete message).
— The BCC calculated for the received characters does not match the 
received character following the ETX.
— The message text is less than three characters, or greater than 13 
(N), 33 (T), or 47 (A) characters.
7. The receiver must respond with a NAK to a received ENQ when the follow-
ing occurs:
— The original ACK/NAK reply has been repeated up to MRR times in 
response to ENQs spaced LAT or less. After MRR retransmission of 
an ACK/NAK, the link will also be dropped.
— The interval since the last response (to a message or to an ENQ) is 
greater than the LAT (assumed missed message).
8. The receiver must increment the expected message count of the sender by 
one after receiving a message modulo (10) (N) or modulo (10) +2 (T) (A). 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
33 Link Setup and Drop Conditions 
Link Setup and Drop Conditions
Link Setup
The PMS, if operational, must have the Data Terminal Ready EIA pin in the “on” 
state. The switch attempts to bring the link up by placing an internal call to the 
extension of the data module connected to the PMS. This call sets the Data Set 
Ready EIA pin to the “on” state which allows the PMS and the switch’s data mod-
ule to “handshake.” The switch will wait up to 12 Link Idle Timer (LIT) periods for 
the PMS to send a status inquiry message before dropping the link. However, if 
the PMS sends ten other messages before the status inquiry message, the switch 
will drop the link. Upon receipt of the status inquiry message, the switch sends a 
status inquiry response and restarts the LIT. Restarts (including power-up) cause 
the switch to attempt link setups within five minutes after switch recovery. The 
switch will immediately retry after most link errors, but will wait five minutes for fur-
ther attempts if the first attempt fails. For protocol error-counter overflow and inter-
nal buffering overflow, the switch will wait five minutes before attempting link 
setup.
Link Drop
The switch drops the physical layer of the link by tearing down the call to the data 
module which causes the data channel to change the Data Set Ready EIA pin to 
the “off” state. However, some data sets may keep the Data Set Ready EIA pin 
“on” which may give the appearance that the physical layer is still “up.”
Ti m e o u t  C o n t r o l
To maintain normal link operations, the PMS must send the switch at least one 
message every LIT period. Otherwise, the LIT will expire causing the link to drop. 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
34 Message Text Format Structure and Encoding 
Message Text Format Structure and 
Encoding
Figure 11 shows the general format for a message packet. Information in the text 
is treated as 8-bit characters. However, these characters are interpreted as either 
two 4-bit encoded digits (nibbles) (N) or ASCII characters (T) (A). Consequently, a 
zero valued most significant bit is used to pad the ASCII character to eight bits. 
Table 3 on page 24
 shows the encoding of the nibbles and the format of the ASCII 
characters (T) (A). Since ASCII characters are supported in some messages, the 
interface supports three modes of the protocol
*:
nThe first mode, normal, uses only nibbles and converts all 0x0 message 
text nibbles into 0xa.
nThe second mode, transparent, uses both nibbles (without 0x0 to 0xa con-
version) and ASCII characters in the message set. 
nThe third mode, ASCII, uses ASCII characters exclusively for the guest 
data (frames 3 through N-2). 
Figure 11. PMS Message Layout
* The Names Registration, Guest Input/Change, and 5-digit RSN feature set require ASCII characters. 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
35 Message Text Format Structure and Encoding 
In transparent mode, the Data Link Escape (DLE) character is used to precede 
any characters in the message text that have a value also used by “control 
characters” (0x00 to 0x1f) to distinguish message text from control characters (for 
example, STX), since 0x0 to 0xa conversion cannot be used. As an example, the 
character sequence “DLE STX” in the message text is interpreted as 0x02 
character value whereas “STX” without the preceding DLE is interpreted as the 
STX control character. The transparent and ASCII modes can use both 4-bit 
encoded nibbles and ASCII characters.
The first two characters immediately following the STX are fixed in format and 
imply the format and length of the remaining message data characters. This 
varies for different message types.
The FEAT CODE character specifies which of the possible variable length feature 
message formats [for example, 11 (N), 31 (T), or 21 (A) for Housekeeper Status 
from Room] applies to the message data. The receiver sets the most significant 
bit of the FEAT CODE to a logical 1 when content errors such as invalid encoding 
for characters interpreted as nibbles, invalid characters for fields interpreted as 
ASCII, invalid coverage paths (T) (A), invalid RSNs (T) (A), and invalid feature 
and process codes exist in the message. Thus, this bit is the VIOL bit and 
indicates a message violation. The receiver returns the invalid message to the 
sender with the violation bit set (VIOL) after inserting its own correct message 
count into the message envelope. For example, a check-in message [FEAT 
CODE = 16 (N), 36 (T), or 26 (A)] from the PMS to the switch will be transmitted 
back to the PMS as a check-in violation message [FEAT CODE = 96 (N), B6 (T), 
or A6 (A)]. Usually, content errors will occur if the sender’s encoding algorithm 
fails or if an odd number of bit errors occur in the same position in different 
characters of the transmitted message.
The receiver of a violation message (that is, the original sender of the invalid 
feature message) has the responsibility to appropriately log the individual violation 
message(s) for later problem determination and correction.
Frame 2 in the normal and transparent mode (the message count [MSGCT] and 
PROC CODE nibbles) consists of two 4-bit encoded digits (Figure 3
, Figure 4, 
and Figure 11
). Frame 2 in the ASCII mode contains only the MSGCT nibble (see 
Figure 5
). The most significant 4 bits, the MSGCT field, represents a message 
counter. The counter is modulo (10) (N) or modulo (10) + 2 (T) (A). The message 
counter complements the ENQ in eliminating acceptance of duplicate messages. 
Such a possibility could occur if an ACK was corrupted to a NAK and the message 
retransmitted; the receiver is expected to notice the immediate repeated message 
count and will ACK the message but will not act on the data. The message 
counter is incremented by the sender with each new message, and not 
incremented when retransmitting in response to a NAK from the receiver. If the 
message count is not what is expected by the switch, the switch logs an internal 
error and resets the message count to the received value. The message counter 
runs from 0 (encoded “A”) through 9 in the normal mode, or 2 through 11 in the 
transparent mode and is relative to the originator. 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
36 Message Text Format Structure and Encoding 
The PROC CODE nibble denotes a “process code.” This code represents a 
specific action or processing for that feature message. In normal mode and 
transparent mode, the PROC CODE is in Frame 2. In ASCII mode, the PROC 
CODE is found in Frame 6.
The (FEAT CODE, PROC CODE) notation is used throughout this document to 
denote a feature message (FEAT CODE) with processing actions (PROC CODE). 
For the ASCII Mode, the FEAT CODE designation (a 2-digit number) is replaced 
by the ASCII equivalent of the feature code. For instance, (13,1) or (MSG,1) 
denotes a message waiting lamp feature, with PROC CODE 1 implying that the 
switch is to turn on the message waiting lamp for an indicated RSN. If only a 
process code is given, the feature code of the section you are in is implied.
The MESSAGE DATA fields, frames 3 through N-2 in the message layout, consist 
of two 4-bit encoded digits per 8-bit character (T) (A), called “nibbles,” with 
encodings or 8-bit ASCII characters. In all message features but one, part of the 
MESSAGE DATA information is the switch RSN. Additional processing 
information may also be passed according to the message feature type.
Null characters are used to pad out message characters where no more data or 
name characters exist. Definitions of null characters used by the normal and 
transparent mode are explained below.
For the Normal Mode, the following encoding rules apply to all message frames 
(any frame between the STX and ETX):
nThe binary nibble 1010 is the encode in MESSAGE DATA fields for 
the0000 nibble; this prevents MESSAGE DATA octets such as 0x02, 0x03, 
0x05, and 0x06 from being confused with STX, ETX, ENQ, and ACK, 
respectively (for example, a message text frame that has value 0x03 would 
be transmitted as 0xa3).
nThe 0xff denotes a null character (not the standard ASCII null 
character 0x00) and will be used to pad out message characters. In a 
frame with only one 4-bit information digit, the null “0xf” nibble pads the 
most significant 4-bit field.
nLeading zeros (encoded 0xa) are used for nibbles of data items that are 
lower in value than the allotted space; for example, RSN 305 will be sent 
as a3a5.
nThe BCC 8-bit octet does not follow the 0x0 -> 0xa encoding rule and thus 
may be 0x02, 0x03, 0x15, etc. It may always be assumed that the charac-
ter received immediately after an ETX is the BCC for the transmitted mes-
sage. 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
37 Message Text Format Structure and Encoding 
For the Transparent Mode, the following encoding rules apply to all message 
frames (any frame between the STX and ETX):
nThe DLE character must precede any control character (valued 0x00 
to 0x1f) in the message text.
nLeading zeros are used for nibbles of data items that are lower in value 
than the allotted space; for example, RSN 305 will be sent as 00305.
nThe 0xff denotes a null character (not the standard ASCII null 
character 0x00) and will be used to pad out frames. In a frame with only 
one 4-bit information digit, the null nibble pads the most significant 4-bit 
field. Name characters, however, will be filled with ASCII space 
character 0x20 for padding the field.
nThe BCC 8-bit octet always follows immediately after an ETX. Any trans-
mitted DLE characters are included in the BCC.
For the ASCII Mode, the following encoding rules apply to all message frames 
(any frame between the STX and ETX):
nLeading zeros are used for nibbles of data items that are lower in value 
than the allotted space; for example, room station number (RSN) 305 will 
be sent as 00305.
nThe 0xf character denotes a null character and will be used to pad out 
frames (such as Frame 2). In a frame with only one 4-bit information digit, 
the null nibble pads the most significant 4-bit field.
nName characters will be filled with ASCII space character 0x20 for padding 
the field.
nThe BCC 8-bit octet always follows immediately after an ETX. Any trans-
mitted DLE characters are included in the BCC.
Ta b l e 5
 shows the message format key and Figure 7, Figure 8, and Figure 9 show 
examples of messages using normal, transparent, and ASCII modes. Figure 12
 
through Figure 22
 show the message formats for each of the feature codes 
(identified as normal, transparent, or ASCII).
Many of the feature messages require that an RSN be specified. This 4-digit (N) 
or 5-digit (T) (A) number is always the switch extension number and sometimes 
correlates identically with the hotel room number. For cases where the hotel room 
and RSN do not correlate, the PMS has the responsibility to perform the room 
number-to-extension number mapping for all messages sent or received over the 
data link.
The use of various feature and process messages and responses is discussed in 
“Feature Codes, Process Codes, and Operations” starting on page 51
. 
						

							DEFINITY ECS and GuestWorks Property Management System
Interface Specifications  555-231-601  Issue 2
December 1999
Feature Description 
38 Message Text Format Structure and Encoding 
Message Text Ordering
The RSN, housekeeper information digits, coverage path, name fields, and 
restriction level consist of several nibbles or characters which have a defined 
ordering.
nRSNs for the normal and transparent modes are mapped from the least 
significant digit to the most significant digit (backwards ordering). For 
example, RSN 72295 maps to the STA5, STA4, STA3, STA2, and STA1 
symbols used in Figure 12
 through Figure 22. In normal mode, there is a 
maximum of 4 digits and 4 nibbles. In transparent mode, there is a maxi-
mum of five digits and five nibbles.
nRSNs for the ASCII mode use forward mapping, with a maximum of 5 dig-
its.
nAll other strings of characters or numbers occur using “forward ordering.” 
Thus, if the user dials the housekeeper FAC followed by 926147, these dig-
its map to the DIG1, DIG2, DIG3, DIG4, DIG5, and DIG6 symbols used in 
Figure 12
 and Figure 13. Similarly, if coverage path 157 is used in a mes-
sage, this number maps to the CP1, CP2, and CP3 symbols used in 
Figure 17
, Figure 19, and Figure 21. Padding is done on the coverage path 
numbers and the housekeeper identification digits.
nThe name characters are ordered as the name is spelled (forwards order-
ing) and are left-justified and padded with space characters as necessary. 
Thus, the name “abc” maps to the symbols used in Figure 17
, Figure 19, 
and Figure 21
 as follows: NAME CHAR1 = a, NAME CHAR2 =b, NAME 
CHAR3 =c, and NAME CHAR4 through NAME CHAR15 = (all blanks).
nIn ASCII Mode, the restriction level value is a 2-digit field. When the restric-
tion level is sent to the PMS, it is sent as “digit-blank.” The switch can 
receive the restriction level in several different ways: 0-digit, digit-blank, or 
blank-digit.
nDID number assignment digits are forward-ordered. If the DID assigned by 
the switch is 21207, the number maps to DID1, DID2, DID3, DID4, and 
DID5. This is shown in Figure 17
.