654
9
9 Communication9.8.3 Soft Element Access Addresses When the H3U PLC Serves as a Slave Station
● Data length: It is the length of the data to be accessed. If the master station will access M0 to M10 (11
elements) of a slave station, the value is 11.
● Master buffer address: It is the head address of the master buffer. As shown in the preceding gure
(No. 1), the master station reads data from the slave station and stores the read data in D100. In this
case, D100 can be accessed in the user program. As shown in the preceding gure (No. 2), the master
station writes values of 100 elements starting with D200 in 100 registers starting with 0.
● Port number: It is 502 by default. Port 502 is specied by Modbus TCP, and you do not need to modify it.
● Station number: It is a serial port number assigned to an Ethernet serial device. It is 255 by default,
and you do not need to modify it.
Note: For each conguration item, there is an upper limit.
Maximum number of
coils to be read
1968
Maximum number
of coil groups to be
written
1936
Maximum number of
registers to be read
123
Maximum number
of registers to be
written
121
Modbus TCP command codes supported by an H3U model
Command Code Function
0x01 Reads coils.
0x02 Reads coils.
0x03 Reads registers.
0x04 Reads registers.
0x05 Writes one coil.
0x06 Writes one register.
0x0F Writes multiple coils.
0x10 Writes multiple registers.
After the Ethernet master station conguration is downloaded, the system automatically creates and
manages connections.
9.8.3 Soft Element Access Addresses When the H3U PLC Serves as a Slave
Station
H3U soft elements can be accessed through Modbus TCP devices. The following table lists addresses of
soft elements.
Coil Addressing
Variable Head address Number of coils
M0-M7679 0 (0) 7680
M8000-M8511 0x1F40 (8000) 512
SM0-SM1023 0x2400 (9216) 1024
S0-S4095 0xE000 (57344) 4096
T0-T511 0xF000 (61440) 512
C0-C255 0xF400 (62464) 512
X0-X377 0xF800 (63488) 256
Y0-Y377 0xFC00 (64512) 256
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