User Manual

“Halo” System: Communication Protocol 970-00002-000
EXI Wireless Systems, Confidential Page 10 of 33 July 27, 1999
3.4.1. RF Communication
RF communication is taking place between Controllers, Elevators, Receivers on the one side an the Tags
on the other. This is two-way communication accomplished on 433.92 MHz in one direction and 307 kHz
in the other.
3.4.2. Weigand Communication
Weigand protocol is used between Controllers, Elevators, Receivers and corresponding RIMs. This is
unidirectional, 2-wire protocol and each line is used to transfer either ‘ones’ or ‘zeros’.
3.4.3. Control Lines Communication
This is again unidirectional protocol. Four lines are used to send information from the RIM to the
Controller, and they can be configured as either individual control lines or to form control code to transfer
different commands to the Controller
3.4.4. EIA-485 Communication
Controllers, Elevators and Receivers can not directly communicate to the Host. They need interface which
enables them to join the network. This interface is RIM and it converts Weigand protocol to the EIA-485
(in one direction, and EIA-485 protocol into Control Lines protocol in the other direction).
This is multidrop differential protocol which supports up to 256 nodes on the bus. The nodes are
communicating over a twisted pair cable and they should be distributed following the bus topology (EIA-
485 standard). The communication speed can be set to 3 different baud rates, 9600, 19200 or 57600 baud,
but this has to be set in the factory prior the system is shipped to the customer. Default baud rate setting is
57600 baud.
Some specifications of this protocol and comparison to the EIA 232 protocol is presented in Table 1.
Table 1
RS232 RS485
Cabling
single ended multi-drop
Number of Devices
1 transmit
1 receive
256 transmitters
256 receivers
Communication Mode
full duplex Half duplex
Max. Distance 50 feet at 19.2 Kbps 4000 feet at 100 Kbps
Max. Data Rate 19.2 Kbps for 50 feet 10 Mpbs for 50 feet
Signaling unbalanced Balanced
Mark (data 1)
-5 V min.
-15 V max.
1.5 V min. (B>A)
5 V max. (B>A)
Space (data 0)
5 V min.
15 V max.
1.5 V min. (A>B)
5 V max. (A>B)
Input Level Min. +/- 3 V 0.2 V difference