User's Manual

Hi-G-Tek Ltd. Microelectronics & Asset Tracking Technology

116

RS 485/232 Communication Protocol

6.1. RS- 485/232 Communication Protocol:

General Description

Communication between the Local Site Controller LSC and the

STAR READER is based on the master/slave approach. The LSC

is the MASTER unit, the READERS are the SLAVE units.

The LSC and the READERS communicate via a RS-485 multi

drop or RS-232 connection. Each READER has its own address,

enabling the LSC to approach each reader individually.

6.2. Physical Layer

6.2.1. Down-link

Down-link is the link from the LSC to the READERS. The link is

RS-485 or RS-232 half duplex. Data rate can be one of the

following: 2400, 4800, 9600, 19200, 38400 BPS. The default rate

is set at 9600 BPS.

6.2.2. Up-link

Up-link is the link from the READERS to the LSC. The link is

RS-485 or RS-232 half duplex. Data rate can be one of the

following: 2400, 4800, 9600, 19200, 38400 BPS. The default rate

is set at 9600 BPS.

6.3. Protocol Flow.

Communication is initiated by a command sent by the LSC to the

READER. The READER executes the command and responds

accordingly. In a long command session, the session is concluded

when the LSC acknowledges the READER within T = 50 msec.

ACK

If the READERS are in sleep mode, the LSC must ensure they are

awakened prior to the initialization of the session. In this case, the

LSC should wait T = 50 msec before sending the main command.