User Manual

“Halo” System: Communication Protocol 970-00002-000
EXI Wireless Systems, Confidential Page 24 of 33 July 27, 1999
6. Signal lines communication
The Weigand protocol which is unidirectional is used to transfer information from the Controller to the
RIM. Some information (mostly Host requests) need to be passed from the RIM to the Controller. There
are 4 signal lines that are used for this purpose and the Controller monitors these lines every 12.8 ms.
There are two modes of operation for the Control lines. When the “Strobe” line is high, the other 3 lines are
treated individually, and when the “Strobe” is low they are treated as a 3-bit command for the Controller.
Signal lines functionality is shown in the Table 8.
Table 9
Strobe Override Unlock Alarm
Functionality
0 0 0 0 Return to normal mode, end any other mode
0 0 0 1 Send current status
0 0 1 0 Send switch settings
0 0 1 1 Start bypass
0 1 0 0 Reset all Tags in the field and reread them
0 1 0 1 Remote reset key press, clears distress alarm
0 1 1 0 Enter Reader mode / acknowledge Tag
0 1 1 1 Retransmit Tag (only until next Tag comes in)
1 0 x x Start Override
1 x 0 x Start Unlock (Controller only)
Start Bypass (Elevator only)
1 x x 0 Start Host alarm
When there is a need to transfer the command to the Controller some timing guidelines must be followed
as illustrated in the Figure 9. This is necessary in order to preserve integrity of command lines and the fact
that even when control lines are reset to their normal state (all 3 high), the Controller needs this
information to operate properly.
After the “Strobe” signal returns to high state, the signals on the control lines should return to their
previous state before the “Strobe” signal become low. They should be returned within 52 ms from the
rising edge of the “Strobe” signal.
NOTE: Receiver is not able to respond to this communication since it has no control input lines