The 484 controller returns a byte count of 5, as follows: 884

2.2.13 20 (14 Hex) Read General Reference
Returns the contents of registers in Extended Memory file (6x) references. Broadcast is not
supported. The function can read multiple groups of references. The groups can be separate
(noncontiguous), but the references within each group must be sequential.
Query
The query contains the standard Modbus slave address, function code, byte count, and error
check fields. The rest of the query specifies the group or groups of references to be read. Each
group is defined in a separate sub-request field which contains seven bytes:
V The reference type-one byte (must be specified as 6)
V The Extended Memory file number-two bytes (1 ... 10, 0001 ... 000A hex)
V The starting register address within the file-two bytes
V The quantity of registers to be read-two bytes
The quantity of registers to be read, combined with all other fields in the expected response,
must not exceed the allowable length of Modbus messages-256 bytes.
The available quantity of Extended Memory files depends upon the installed size of Extended
Memory in the slave controller. Each file except the last one contains 10,000 registers,
addressed as 0000 ... 270F hexadecimal (0000 - ... 9999 decimal).
For controllers other than the 984-785 with Extended Registers, the last (highest) register in the
last file is:
For the 984-785 with Extended Registers, the last (highest) register in the last file is shown in
the two tables below.
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Examples of a query and response follow. An example of a request to read two groups of
references from slave device 17 is shown. Group 1 consists of two registers from file 4, starting
at register 2 (address 0001). Group 2 consists of two registers from file 3, starting at register 10
(address 0009).
Response
The normal response is a series of sub-responses, one for each sub-request. The byte count field
is the total combined count of bytes in all sub-responses. In addition, each sub-response
contains a field that shows its own byte count.
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