22
02 is the number of bytes of data to be read.
80 is the high byte of data read, it indicates Watchdog Error
00 is the low byte of data read, it indicates that does not have alarms in the low byte.
A4 40 is the CRC.
Also, the Latched alarms can be cheeked with bit mode with Coils. The bit-interpretation of this error
is shown below, the coils 0x200 to 0x20E are not used, but it can be read without limitation:
Coil 0x20F
MODBUS Watchdog
Example: reading latched alarms with coils when watchdog alarm has been activated:
The received message is: 30 01 01 01 9E B4
Where:
30 is the slave address.
01 is the function used. Read Coils.
01 is the number of bytes of data to be read.
01 indicates that the alarm has been activated.
9E B4 is the CRC.
The way to reset the alarms is setting by 0 the holding register 0x20.
Example, reset all the alarms:
Transmitting message: 30 10 00 20 00 01 02 00 00 F8 A1
Where:
30 is the slave address.
10 is the function used. Write multiple registers.
00 20 is the address of the first Holding Register to be set.
00 01 is the number of Holding Register to be set, 1 in this case.
02 is the number of bytes of data sent.
00 00 is the data send. (0 to set to 0 the alarms).
F8 A1 is the CRC.
8.1.11.
CHECKING INSTANTANEOUS ERROR REGISTER
Whenever errors exist, the less significant bit in the Status Input Register 0x00 is set to 1.
Furthermore, for having a more detailed information on the error occurred, these can be requested
to the Input Register 0x01, or reading from Digital Input 0x010 to 0x01F, in this case, as only the
Watchdog alarm is implemented, the Digital Input 0x01F is the only alarm that can change to 1. (It
corresponds to the watchdog alarm).
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