Specifications

Appendix C - Glossary of Terms RS-422 And RS-485 Applications Ebook
Page 104 of 137 Manual Documentation Number: <DocNumber>
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Data Bits
Number of bits per byte. Standard ASCII usually uses 7 data bits. Sometimes 8
data bits are used to accommodate the extended ASCII character set. For
example, Modbus ASCII messages use 7 data bits. Modbus RTU messages use
8 data bits.
Data Line Isolation
Isolation between the signal line input and output, and between the signal line
common/ground on the input side and output side. Isolation is rated in volts of
isolation between all inputs/outputs and signal grounds/commons on one side
compared to the other.
Data Lines
The lines that carry digital data in a computer bus or data communications link
or network. In serial data systems such as RS-232 the data lines are TD
(transmit) and RD (receive). RS-422/485 four-wire networks use two lines:
TDA(-)/TDB(+) for transmit, and two lines: RDA(-), RDB(+) for receive. Two-
wire RS-485 networks use two bi-directional data lines: DATA A(-) and DATA
B(+). Data lines require a signal ground/common to reference the signals.
Even differential data lines should be provided with a reference common wire
connection.
Data Rates
Supported baud rates in bps (bits per second) or transfer rates for other
devices.
DB25
25 pin "D" type connector (looks like a sideways D) The top row has 13 pins
(or holes for pins), the bottom has row has 12 pins (or holes for pins). If the
connector has pins, it is a plug (historically called a male connector); if it has
holes to accept pins, it is a receptacle (historically called a female connector).