MA-033 Rev. 14.0, 12-Nov-18
Hydran* 201i Instruction Manual
Table J - 13: Writing of Data Registers with the Address 1 & 2
J.3.2 Exception Response
Programming or operation errors usually occur due to illegal data detection in a
packet. These errors result in an exception response from the slave. The slave detecting
one of these errors sends a response packet to the master with the high- order bit of the
function code set to 1. The exception codes are described in Table J - 14 below.
The function code is unknown by the server.
The server failed during the execution. The
server was unable to accept the MB Request
PDU. The client application has the responsibility
of deciding if and when to re-send the request.
Table J - 14: Description of Exception Codes
J.4 Hydran 201Ti Data Model
The Modbus protocol only supports very basic data types. Manufacturers combine
registers to be able to represent more complex types of data such as floating point, time-
stamped, event files, logs, etc. The Modbus standards do not define how this is done and
that becomes an obstacle for interoperability between systems. Modbus bases its data
model on a set of four tables that reflect simple data types (see Table J-15 below).
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