91
Table 5.1.15.1.-4 Possible exception codes
Code Name Description
01 Illegal function The slave does not support the requested function.
02 Illegal data address The slave does not support the data address or the
number of items in the query is incorrect.
03 Illegal data value A value contained in the query data field is out of range.
04 Slave device failure An unrecoverable error has occurred while the slave
was attempting to perform the requested task.
If an Illegal data value exception response is generated when
attempting to preset multiple registers, the contents of the register to
which an illegal value has been imposed and of the following registers
is not changed. Registers which have already been preset are not
restored.
User-defined registers
Reading of unwanted data in a data block wastes bandwidth and complicates data
interpretation. For optimum efficiency in Modbus communication, data has
therefore been organized into consecutive blocks. In addition, a set of programmable
user-defined registers (UDR) has been defined in the holding register area.
The first sixteen holding registers, that is, HR1...16, are user-defined registers. The
UDRs can be linked to any holding register, except for HR721...727, using SPA
parameters 504V1...504V16. However, one UDR cannot be linked to another, that
is, linking cannot be nested. Each parameter contains the address of the holding
register to which the UDR is linked.
If a UDR is linked to a non-existent holding register, reading from the register fails
and an Illegal address exception response is sent. Giving the link address
the value 0 disables the UDR. If the master reads from a disabled UDR, the value 0
is returned.
The UDRs are mirrored in HR385…400.
Fault records
The data recorded during a fault sequence is called a fault record (FR). The slave
stores the five latest fault records. When a sixth record is stored, the oldest record is
deleted.
Feeder Protection Relay
Technical Reference Manual - ANSI Version
REF610REF610
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