0x8101

33025

Illegal Function

The function code received in the query is not an allowable action for the server (or slave). This may be because the function code is only applicable to newer devices, and was not implemented in the unit selected. It could also indicate that the server (or slave) is in the wrong state to process a request of this type. This code is also returned when attempting to write to a read-only attribute.

0x8102

33026

Illegal Data Address

The data address received in the query is not an allowable address for the server (or slave). More specifically, the combination of reference number and transfer length is invalid.

0x8103

33027

Illegal Data Value

A value contained in the query data field is not an allowable value for server (or slave). This indicates an invalid request structure. It specifically does NOT mean that a data item submitted for storage in a register has a value outside the expectation of the application program, because the MODBUS protocol does not test the significance of any particular register value.

0x8104

33028

Slave Device Failure

An unrecoverable event occurred while the server (or slave) was attempting to perform the requested action.

0x8105

33029

Acknowledge

Specialized use in conjunction with programming commands: The server (or slave) has accepted the request and is processing it, but a long duration of time will be required to do so. This response is returned so that a timeout in the client (or master) will not occur. The client (or master) can next send a Poll Program Complete message to determine if processing is completed.

0x8106

33030

Slave Device Busy

Specialized use in conjunction with programming commands: The server (or slave) is engaged in processing a long–duration program command. The client (or master) should retransmit the message later when the server (or slave) is free.

0x8107

33031

Negative Acknowledge

Specialized use in conjunction with programming commands: The request attempts to initiate a program function that is not supported by the server (slave).

0x8108

33032

Memory Parity Error

Specialized use in conjunction with function codes 20 and 21 and reference type 6, indicating that the extended file area did not pass a consistency check.

0x810A

33034

Gateway Path Unavailable

Specialized use in conjunction with gateways, indicates that the gateway was unable to allocate an internal communication path from the input port to the output port for processing the request. Usually means that the gateway is misconfigured or overloaded.

0x810B

33035

Gateway Target Device Failed to Respond

Specialized use in conjunction with gateways, indicates that no response was obtained from the target device. Usually means that the device is not present on the network.