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920MHz Band Wireless Device (Korea) USERS MANUAL EM-9121 Rev. 1
7.1.10 STATION NUMBER AND SHORT ADDRESS
To collect data from remote I/Os connected to wireless devices, it is necessary for a parent device to associate short addresses set
to child devices with Modbus station numbers of the remote I/Os by either of following methods.
• List mode
• Range mode
Select a mode as shown in the table below.
[Table 7.12] Setting mode of short address
DEVICE
SETTING
SPECIFICATIONS / RANGE
REMARKS
Parent
Required
List mode
Range mode: max. No. of multi-drops of 1 device
Range mode: max. No. of multi-drops of 1 to 4 device
Range mode: max. No. of multi-drops of 1 to 8 devices
Range mode: max. No. of multi-drops of 1 to 16 devices
Range mode: max. No. of multi-drops of 1 to 31 devices
■
LIST MODE
The list mode is a method to register the combination of the Modbus station numbers and the short addresses of the child devices
on the station number list of the parent device.
1) Modbus station number
Set station numbers of the Modbus devices connected to the child devices.
2) Short address
Set short addresses to the parent and child devices. The address of the parent device is fixed to 0000.
Set short addresses to the child devices within the range of 0001 to FFFD in 4-digit hexadecimal.
Set the short addresses so as not to overlap with each other.
3) Registration of the station numbers and the short addresses of the child devices
Register the combination of the short addresses of the child devices and the station numbers of the Modbus devices on the sta-
tion number list of the parent device.
■
RANGE MODE
The range mode is a method to assign the station numbers of the Modbus devices to the short addresses of the child devices within
the specified range.
1) Max. No. of multi-drops
Set to the child devices capable of multi drop connection.
Decide the max. number, to be set to the parent device, of devices to be connected based on the number of devices actually
connected in multi-drop in the network.
Select among 1, 1 to 4, 1 to 8, 1 to 16, and 1 to 31 devices so as to be greater than the number of devices actually connected.
2) The number of devices to be connected
The configurable station numbers depend on the max. No. of multi-drops set to the parent device.
A part of the range of configurable station numbers is as shown in the table below.
[Table 7.13] Range of configurable station numbers
SHORT ADDRESS OF
CHILD DEVICE
Max. No. of multi-drops
CONFIGURABLE STATION NUMBER
1
4
8
16
31
0001
1
1 – 4
1 – 8
1 – 16
1 – 31
0002
2
5 – 8
9 – 16
17 – 32
32 – 62
0003
3
9 – 12
17 – 24
33 – 48
63 – 93
0004
4
13 – 16
25 – 32
49 – 64
94 – 124
0005
5
17 – 20
33 – 40
65 – 80
125 – 155
0006
6
21 – 24
41 – 48
81 – 96
156 – 186
0007
7
25 – 28
49 – 56
97 – 112
187 – 217
0008
8
29 – 32
57 – 64
113 – 128
218 – 247
*
1
0009
9
33 – 36
65 – 72
129 – 144
000A
10
37 – 40
73 – 80
145 – 160
*
1. Modbus protocol allows up to 247 child devices to connect.
3) Short address and Station number
Set short addresses to the parent and child devices. The address of the parent device is fixed to 0 (0x0000).
Set the short addresses of the child devices after deciding the station numbers of the connected Modbus devices as described in
the above “2) The number of devices to be connected”. Those child devices not connected to the Modbus devices (repeaters) are
not required to have station numbers. Set their addresses arbitrarily within the range of 4096 (0x1000) to 65533 (0xFFFC) so as not
to overlap with those of other child devices.
