Delta RMC101 - Manual (Page 500)

RMC100 and RMCWin User Manual
5-250
Resistance 48kW ||
48kW
= 118W
Then, we calculate how much DC resistance the network has between power rails:
Total
Resistance
= 1150W +
118W +
1150W
= 2418W
Next, we calculate how much current is flowing through this DC resistance:
Current = 5VDC /
2418W
= 2.068mA
Finally, we calculate the voltage drop across the termination resistor:
Voltage = 2.068mA *
118W
= 244mV
This value is greater than the ±200mV difference required by the TIA/EIA standards and constitutes a
valid binary 0 state.
5.5.3 RMC SERIAL Protocols
5.5.3.1 Using Modbus/RTU with the RMC SERIAL
Modbus/RTU is a standard protocol managed by Schneider Automation (Modicon). The
specification is available through Schneider Automation (http://www.modicon.com/openmbus)
and Modbus.org (http://www.modbus.org). The Modicon Modbus Protocol Reference Guide (PI-
MBUS-300) from Modicon is a good reference for this protocol. It is available through the
Modicon web site. At the time of this writing it was necessary to select the MODBUS/TCP
Protocol
documents link to find an Acrobat Reader (.pdf) format version of this document.
Modbus, in its various forms such as Modbus/ASCII, Modbus/RTU, Modbus Plus, and
Modbus/TCP, is a request/response protocol. That is, a Modbus master makes a request from a
Modbus slave, and the slave responds. A number of functions are defined under Modbus. The
following functions are supported by the RMC SERIAL module: