Page 10 NDA-30115 Revision 1.0
Architecture Property Management System - Communication Interface
Timers The 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 timeou t occ urs d uri ng th e tr ansmiss ion
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 seq uence 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 ti meout occurs, t he sender l oses
send rights.
Cabling
Considerations When 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
Characteristics The characteristics of the signal s transmitted acro ss the communications l ink are as
follows:
1FG
SD
RD
RS
CS
DR
SG
CD
ER
2
3
4
5
6
7
8
20
FG
SD
RD
RS
CS
DR
SG
CD
ER
1
2
3
4
5
6
7
8
20
Pin No. Signal Cable Signal Pin No.
NEAX PMS