Advantech EKI-1221D User Manual page 13

data to be sent, and an error-checking field. The slave's response message, which is
also constructed using Modbus protocol, contains fields confirming the action taken,
any data to be returned, and an error-checking field. If an error occurred in receipt of
the message, or if the slave is unable to perform the requested action, the slave will
construct an error message and send it as its response.
The basic system architecture is as below:
Figure 2.1 Modbus System Architecture 1
Figure 2.2 Modbus System Architecture 2
7 ADAM-4572 & EKI-122X Series User Manual