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TCP/IP frame
(ii)
Over the TCP/IP network, the MBAP generates the function code field and data field, as shown
in Figure 11.4-10.
Address field of IED:
The TCP/IP frame includes the IP header, so the address of the IED is identified with
the IP address.
IP Header
Figure 11.4-10 Message frame over TCP/IP link
Note: The block—function code and data fields—is called "Protocol data unit
Function code field and Data field:
The fields are used for a query/response command code and its data. The filed
content is the same as the Modbus RTU one (see Figure 11.4-7).
8 bits
Function code field
MDAP header
Ethernet frame
Modbus TCP layers
(PDU)". The Data link layer add an IP header and another one—
Modbus application protocol (MBAP) header
- 925 -
MBAP data
N×8 bits
Data field
Data
.
6F2T0207 (0.01)
Application
Presentation
Session
Transport
Network
Data link
Physical
OSI layers
called
GRE200 (5,6)
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