Function code 65

Some PLC's are able to understand function code 65, which is a non-standard Modbus function code. One type of PLC that understands function code 65 is called an HTMUX box. If such a PLC receives function code 65, it knows that a 4-byte floating point should be returned.

Each register that can be read with function code 65 contains 4 bytes of information. Standard registers can hold only two bytes of information. Function code 65 is similar to data type 4 above, except that there is no need to map a single register to two different registers. Each register can already hold 4 bytes.