Addressing I/O extension modules and RAD-900-DAIO6 with Modbus RTU
3827_en_B PHOENIX CONTACT 113/138
Error codes and formats for Pt 100 values
Table 9-9 Representation of the RAD-PT100-4-IFS Pt 100 values
9.7 RSSI signal register
The RSSI values indicate the received signal strength on the wireless module. In both
PLC/Modbus RTU and PLC/Modbus RTU dual modes, you can read the RSSI values via
the serial interface of the master wireless module (RAD ID = 01) using Modbus/RTU com-
mands. The RSSI values of all wireless modules are within the address area
35001 ... 35250.
Table 9-10 RSSI signal register
– Bits 8 ... 15 are reserved.
– Values < 255 indicate the RSSI value in -dBm.
– The value 255 means that the RSSI value is invalid or the device cannot be reached.
Example for reading the RSSI register of the station with RAD ID = 2:
function code 04, start address 5001 (hex1389)
Data word RAD-PT100-4-IFS
Pt 100 input
RAD-AO4-IFS
analog output
hex dec / error code -50°C ... +250°C 0 mA ... 20 mA 0 V ... 10 V Possible cause
0000 0 -50°C 0 mA 0 V
7530 30000 +250°C 20 mA 10 V
7F00 32512 +275.12°C 21.67 mA 10.84 V
8001 Overrange
8002 Open circuit Sensor wired incorrectly,
measuring line too long,
cable resistance too high
8080 Underrange
Address area 35001 ... 35250
Modbus function code fc 04
Address Wireless module High byte Low byte, RSSI value
15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
35001 RSSI - RAD ID = 1
(master)
Reserved X X X X X X X X
35002 RSSI - RAD ID = 2 Reserved X X X X X X X X
... ... Reserved X X X X X X X X
35250 RSSI - RAD ID = 250 Reserved X X X X X X X X
In PLC/Modbus RTU dual mode, the RSSI value is also within the register 35000 of each
wireless module, since each one has its own Modbus address.
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