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ADAM-4572 & EKI-122X Series User Manual
8
2.1.2
Modbus RTU
The Modbus/RTU protocol defines how a “master” device polls one or more “slave”
devices to read and write data in real-time over RS-232, RS-422, or RS-485 serial
data communication.
When using RTU mode, each 8-bit byte in a message contains two 4-bit hexadecimal
characters. The main advantage of this mode is that its greater character density
allows better data throughput than ASCII mode for the same baud rate. Neverthe-
less, each message must be transmitted in continuous stream.
2.1.3
Modbus ASCII
When using ASCII mode, each 8-bit byte in a message is sent as two ACSII charac-
ters. The primary advantage of this ASCII mode is that it allows time intervals of up to
one second to occur between characters without causing an error.
2.1.4
Modbus TCP
As a new extension of Modbus/RTU, the Modbus/TCP protocol defines how Modbus/
RTU messages are encoded within and transported over TCP/IP-based networks.
Modbus/TCP is just as simple to implement and flexible to apply as the original Mod-
bus/RTU. The Modbus/TCP protocol is defined by its form of encapsulation for a
Modbus request or response. That means the Modbus request or response data is
encapsulated in TCP frame that has a six-byte header in Modbus/TCP protocol.
Modbus/TCP enables the use of Modbus messaging in an Intranet running the TCP/
IP protocols. Modbus/TCP is most commonly used for Ethernet attachment of PLC’s
or I/O modules to other simple field buses or I/O networks.
Table 2.1: Comparison of Modbus RTU and ASCII Modes
Mode
RTU
ASCII
Coding System
8-bit binary.
Two hexadecimal
character contained in
each ASCII character of
the message
Hexadecimal.
One hexadecimal
character contained in
each ASCII character of
the message
Bits per Byte
1 start bit,
8 data bits,
1 bit for even/odd parity;
no bit for parity
1 stop bit if parity is used;
2 bits if no parity
1 start bit ,
7 data bits,
1 bit for even/odd parity;
no bit for parity
1 stop bit if parity is used;
2 bits if no parity
Error Check
CRC
LRC
Содержание ADAM-4572
Страница 1: ...User Manual ADAM 4572 EKI 1221 EKI 1222 EKI 1224 EKI 1221D EKI 1222D 1 2 4 port Modbus Gateway...
Страница 7: ...Chapter 1 1 Introduction...
Страница 10: ...ADAM 4572 EKI 122X Series User Manual 4...
Страница 11: ...Chapter 2 2 Getting Started...
Страница 20: ...ADAM 4572 EKI 122X Series User Manual 14 Figure 2 5 Back View of EKI 1221 Figure 2 6 Top View of EKI 1221...
Страница 22: ...ADAM 4572 EKI 122X Series User Manual 16 Figure 2 9 Back View of EKI 1222 Figure 2 10 Top View of EKI 1222...
Страница 24: ...ADAM 4572 EKI 122X Series User Manual 18 Figure 2 13 Back View of EKI 1224 Figure 2 14 Top View of EKI 1224...
Страница 26: ...ADAM 4572 EKI 122X Series User Manual 20 Figure 2 17 Back View of EKI 1221D Figure 2 18 Top View of EKI 1221D...
Страница 28: ...ADAM 4572 EKI 122X Series User Manual 22 Figure 2 21 Back View of EKI 1222D Figure 2 22 Top View of EKI 1222D...
Страница 34: ...ADAM 4572 EKI 122X Series User Manual 28 Figure 2 32 DIN rail Adapter Figure 2 33 DIN rail Mounting...
Страница 38: ...ADAM 4572 EKI 122X Series User Manual 32...
Страница 39: ...Chapter 3 3 Configuration...
Страница 46: ...ADAM 4572 EKI 122X Series User Manual 40...