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Page 4 NDA-30115 Revision 1.0
Architecture Property Management System - Communication Interface
Asynchronous Transmission
Line Control
Characteristics
The 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)