Chapter 6 Communication Mode
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Function code 0x04 (Read Input Registers)
The function code 04 is a query to read input register of slave apparatus. Broadcasting is not supported.
(1) Sending data area format
Sending data area requires 4 words. Please set 6 bytes for head word.
Figure 6.38 Sending data area format (Function code 0x04)
1) Device No.: Set the slave number by hexadecimal number. (H01 to HFF. H00 cannot be used.)
2) Function code: Set the function code to H04.
3) Starting address: Set the starting address of input register by hexadecimal number. (H0000 to HFFFF)
4) Number of input registers : Set the number of input registers by hexadecimal number. (H0000 to H00FE)
Ex.) Reading the value of 104 input registers from the address 30464 of slave No.14.
The head address of Sending data area WR100
WR100 = H0006
WR101 = H0E04
WR102 = H01CF
WR103 = H0068
(2) The state of receiving data area
1) Completed properly
Figure 6.39 Receiving data area format (Function code 0x04)
When a response is received properly from the slave, completion flag (t+1) will be ON, and the input register
information is stored in the address specified by the query from head word.
2) Receiving exception response
When an exception response is received, error flag (t+2) turns on, and the receiving data area is as follows.
Figure 6.40 Receiving data area format (Function code 0x04 / Exception response)
3) Other errors (except for exception response)
When there is no response from a slave or an abnormal factor is detected in the response, error flag (t+2) turns on,
an error code is stored in the return code area of the s parameter, and the number of receiving data is cleared to
H0000. (Data other than the number of receive data bytes maintains previous values.)
Please refer to section “6.3.5 Error detection in modbus master mode” for more information on error codes.
Exception code
Number of receive data (H0002)
H 8 4
Number of receive data (bytes)
Input register 1
1 word
…
Input register n
Number of input registers
Device No.
0 4
Starting address
H 0 0 0 6
1 word
04: Function code
Starting address of input register to read
The number of the input registers to read
Summary of Contents for EH-150 Series
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Page 10: ...M E M O ...
Page 30: ...Chapter 4 Installation 4 10 M E M O ...
Page 156: ...Chapter 7 System setup 7 12 M E M O ...
Page 164: ...Chapter 8 Daily and Periodic Inspection 8 8 M E M O ...
