Table J - 4: Function codes
In order to promote the interoperability of systems, the coils and discrete inputs are
accessed as the same digital data objects. For the same reason, the input and holding
registers are also accessed through the same 16-bit data objects. An unsupported
function code addressed to the Hydran 201Ti slave returns an Illegal Function Code
exception response code of 01; see Section J.3.2 on page 252 for more details.
J.3.1.1 Read Coils (01h) / Read Discrete Inputs (02h)
This function is used to read a binary value. Up to 2,000 (07D0h) consecutive binary
can be read per request. Table J-5 shows the format of the master and slave packets.
Note: This Section demonstrates how to build and understand a 01h or 02h Modbus
request/response exchange. To read or write Hydran 201Ti’s digital data values,
please refer to the subsequent Sections.
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