Micromod MOD: MODBUS RTU Communications Guide Manual do Utilizador descarregar pdf (Página 29)

MODBUS RTU

COMMUNICATIONS GUIDE

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.

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