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6 Interface
The interface to the Weather Station consists of a RS485 link (half-duplex mode), with the following
data format:
•
9600baud (the baud rate can be selected with the
).
•
8data bits.
•
No parity.
•
1stop bit.
•
Data in binary format (command interpreter: MODBUS RTU).
The behavior (configuration) of the Weather Station can be changed using the available commands
(see
).
When the Weather Station starts up, the character string "Weather Station", software version,
hardware version and serial number is output:
Weather Station
v03.04
508990 v11-11
12030123
6.1 Command interpreter MODBUS RTU
Once the command interpreter is selected the transmitted bytes are interpreted according to the
MODBUS specification (http://www.modbus.org/). Here, the weather station FS6003 is representing
a MODBUS Slave.
The data transmission is carried out in packages, so-called frames, of maximum 256 bytes. Each
package contains a 16bit CRC checksum (initial value: 0xffff).
Slave-Address
Function code
Data
CRC
1byte
1byte
0...252byte(s)
2bytes
CRC low-byte
CRC high-byte
Table 1 : MODBUS Frame
The following MODBUS functions are supported:
-
0x04 (Read Input Register).
-
0x03 (Read Holding Registers).
-
0x06 (Write Single Register).
-
0x10 (Write Multiple Registers).
The weather station FS6003 supports a write access for the slave-
address 0 (“Broadcast”).
All received MODBUS request are checked for validity before carrying out. In error case the
weather station responds with one of the following exceptions (
MODBUS Exception Responses).
