Micromod MOD: MODBUS RTU Communications Guide - Manual (Page 29)

MODBUS RTU
COMMUNICATIONS GUIDE
25
GLOSSARY
The following terms are defined as they relate to this document. The definitions given here may not be the
same throughout the industry.
Alias A meaningful short-hand name given to a data point
Baud Serial communication data transmission rate
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)
CL block Configured List block
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.
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”.
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 A 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)
Live Zero Indicates that a numeric range contains both positive and negative
numbers
Loopback A test used for checking functionality of a serial port, utilizing a test plug
that connects send, receive and handshaking signals
Long Integer Analog value consisting of two consecutive 16-bit registers
ML block MODBUS List block
MLP MultiLoop Processor (Modcell 2000 Series Controller)
MSC block MODBUS Serial Communications block
Parity Simple method of data error checking performed at the byte level. May be
user-specified as Odd, Even or None with most equipment and software.