LSIS XGL-EFMTB - Page 160

Chapter 8 Dedicated Communication
8-20
Modbus function and the maximum number of response data that Modbus TCP driver supports
are described in the table below. The correspondent master device shall make a request within
the range specified in the table. For example, Bit Read Request is available up to 2000 bits, and
Bit Write Request is up to 1600 bits.
Code
Description
Address
Response Size
01
Read Coil Status
hXXX
2000 Coils
02
Read Input Status
1XXXX
2000 Coils
03
Read Holding Registers
4XXXX
125 Registers
04
Read Input Registers
3XXXX
125 Registers
05
Force Single Coil
hXXX
1 Coil
06
Preset Single Register
4XXXX
1 Register
15
Force Multiple Coils
hXXX
1600 Coils
16
Preset Multiple Registers
4XXXX
100 Registers
[table 8.3.1] Modbus function code
Mapping of XG-T PLC memory is required for each function code’s request.
Respective setting details are as follows;
Item
Description
Remarks
DI area address
XGT address applicable to digital input area
Bit address
DO area address
XGT address applicable to digital output area
Bit address
AI area address
XGT address applicable to analog input area
Word address
AO area address
XGT address applicable to digital output area
Word address
The address value specified in each item is the base address of the applicable area.
Fig 8.3.1 shows that DI area is assigned starting from PX0000 and that AO area is assigned
starting from PW300.
The input value of the base address shall be within the effective areas of %M, P, etc. Since
Modbus address is 1 ~ 9999 (decimal), the size of the bit I/O area will be 9999/8 = 1249.875
bytes. In addition, the size of the word I/O area will be 9999*2 = 19998 bytes.
If the user sets the base address of the bit output (hXXX) area to 0, Modbus bit area 00001 will
be correspondent to 0
th
byte, 0
th
bit, and 00002 to 0
th
byte, 1
st
bit.