RS485 networks are ideally suited to networked access control systems, but great care has to be taken to ensure that the network will function correctly.

A problem with the RS485 network is the major reason for system problems.

Taking care to get the network functioning correctly should always be the first priority.

How does the system work?
Communication between PC and doors functions as follows. Every so often (usually 2 - 10 seconds) the computer communicates with the door controllers. This is called a poll. The delay between polls is called the polling interval. Each door controller on the networked is polled in turn. ie door 1, then door 2 etc.

For firmware versions pre V7.0 (before 1st December 2004) door controller will not answer a poll if it is busy doing any of the following:

• reading a card
• opening the door after a card read
• opening a door after an egress button press
• the door has not been closed after a valid card read or egress
• the door ajar timer is still running (older versions of firmware only pre March 2000)

These are valid reason for a door controller not to respond. The last point can be a cause of conern in some applications, since as well as not responding to a poll the controller will not read another card until the door held timer has timed out. The time period can be adjusted in the Door Setup window of the software. If this is a problem the firmware can be upgraded to version 7. Please contact SRS Sales for more information email : sales@doorentrydirect.com

On every poll from the computer the door controllers will respond by sending their transactions (ie events which occur at each door) back to the computer. This information is then displayed on the computer screen.

NOTE: When waiting for a controller to respond you should allow a few minutes. A controller with 457 event to send will take about 35 seconds to send the data. You may have to allow this time for each controller on the network if the computer has been switched off or not communicating for a while.