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FG_F6_MODBUS_EN_01 / 2020-06-17
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Direct access
In Direct access, the master can only access to bits one by one.
Example for reading the state of the “Chaining” bit (word 1, bit 14):
Master
Slave
—
Make a
Read N*words
request of 1 word at the
241Fh
address.
On network:
01
03
24
1F
00
01
BF
3C
01
Slave address
03
Function number (Read N*words)
24 1F
D.A. address of the “Chaining” bit
00 01
Number of words to read
BF 3C
CRC
—
Answer to the request:
On network:
01
03
02
01
00
B9
D4
01
Slave address
03
Function number (Read N*words)
02
Number of read bytes
01 00
Word: read 0001h (Chaining bit = 1)
B9 D4
CRC