Eaton easyE4 - Page 795

10. easyE4 communication Connection to other devices
10.17 Modbus TCP
Read Coils 0x01:
This function reads the entered number of bit outputs starting from a specified start-
ing address and then returns the result in bytes (8 outputs per byte)
Function Code
1 byte
0x01 ;Read Coils
Start address
2 byte
Must always be 1 less than the starting output you want
(zero-based)
Number of out-
puts
2 byte
1 to 2000 (0x7D0)
Tab. 135: Request-PDU
Response to the request being received
1. The starting address is analyzed (distributed among bytes 1 and 2)
a. Byte 1 = Hi; Byte 2 = Lo
2. The number of outputs is analyzed (distributed among bytes 3 and 4)
a. Byte 3 = Hi; Byte 4 = Lo
3. The output states are read
a. From the start of the (starting address) to (starting address + number of
outputs)
Function Code
1 byte
0x01 ;Read Coils
Bye Count
1 byte
N
Output values
n * 1 byte
value
Tab. 136: Response-PDU
n= Number of outputs read / 8
Preparation for sending the response
1. The read bits are encoded in bytes
(1 but per output state; 1=ON, 0=OFF)
2. The LSB of the first byte, i.e., bit 0, contains the state of the output that is
addressed first in the request. The other outputs follow in ascending order.
3. If a byte is not used fully, the unused bits will be padded with 0's.
Once the response is encoded, it is sent.
easyE402/24 MN050009ENEaton.com
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