Elmo DBP SERIES manual System Operation RS485 and Checksum Protocol, Current Control

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4. System Operation

4.1 RS485 and Checksum Protocol

The RS485 in the DCB is configured as 8-bit, no parity, 1 stop bit, half duplex. The following baud rates are available: 300, 600, 1200, 2400, 4800, 9600, 19200, 38400, 57600. No hardware handshaking is required.

In the RS-485, which is a Half Duplex system, all the Transmitters and all the Receivers share the same Multidrop wire. Therefore, each character that is transmitted on the line, is automatically received by all the Receivers. This is an inherently "confused" way to transmit data and no "Echo" procedure can assure reliable communication.

In order to solve this reliability problem, it is necessary to use standard protocols procedures.

It is important to understand that using RS485 with the DCB products without any protocol is possible. This is also the default condition whenever the RS485 is activated. However, the reliability of the communication is only assured when activating the protocol. This is done by sending the command CK1 from the host to the DCB.

Chapter 1.2.1 in the DCB Software manual explains the standard protocol used and supplied by Elmo.

4.2 Current Control

The analog part of the DBP is actually a standard amplifier that operates in current mode. However, the DCB receives continuously analog information about the current magnitude, direction and ripple. This information is processed to obtain digital control of the following features:

*Continuous current limit

*Peak current limit

*Time dependent peak current limit

*Current ripple

DBP - Rev 6/93