20 - Appendix
RS485
8 Appendix
8.1 List of abbreviations
ASCII
American Standard Code for Information Interchange
Baud rate
Unit for measuring transmission speed in bits/s;
Bit
A binary digit, representing a one or zero
Bus
An electrical circuit over which data is transmitted
Byte
A whole number value represented by eight bits (0 to 255)
Chassis or Chassis Ground A connection to an electrically conductive housing or frame
of a device. It may or may not be connected to Earth
Ground.
Coil
The telegram structure for Modbus transmission is
implemented in registers (WORD) or coils (bits). A coil may
be either 8 or 16 bits in length.
Common
The voltage reference point of a circuit. It may or may not be
connected to earth ground, though it is generally assumed to
be at zero volts, unless otherwise indicated. In floating
circuits, the common is sometimes at a relatively high
potential. This term is sometimes used interchangeably with
the term “Ground” or GND.
CRC
Cyclic Redundancy Check. Complex error checking on a
message block.
CTS
ClearToSend hardware handshaking signal. Used with
RequestToSend.
Earth or Earth Ground
Global zero voltage reference point. Physical connection is
made to the earth through a grounding rod, water pipe or
other reliable connection.
Ground Voltage reference point of a circuit
It may or may not be connected to earth ground, though it is
generally assumed to be at zero volts. Sometimes used
interchangeably with the term “Common”.
Handshaking
method of data flow control for serial communications
Hexadecimal or HEX
A number system using a decimal 16 as its base. A single
digit number in HEX ranges from 0 to 15, represented by 0
to 9 and A to F.
HMI
Human-Machine Interface (formerly MMI)
Industrial
IT
Umbrella concept for ABB’s vision for enterprise automation.
Industrial
IT
Architecture
The architecture of the Industrial
IT
system. The architecture
defines how the system is built, in terms of basic concepts,
underlying technologies, system topology, modularity, and
mechanisms for interaction between different parts of the
system. It also defines concepts, rules, and guidelines that
a component must comply with in order to fit in the
Industrial
IT
system. A central feature of the IIT architecture is
