Elmo SERVO AMPLIFIER DBP SERIES - Manual (Page 18)

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DBP - Rev 6/93
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