E.14
SEL-787 Relay Instruction Manual Date Code 20081022
Modbus RTU Communications
Communications Protocol
The Parameter Descriptor field is defined in Table E.21.
The Parameter Conversion field is defined in Table E.22.
Use Table E.23 to calculate the actual (not scaled) value of the parameter
(setting):
Equation E.1
Use Table E.23 to calculate the scaled setting value:
Equation E.2
The relay response to errors in the query are shown Table E.23.
Table E.21 60h Read Parameter Descriptor Field Definition
Bit Name Description
0 RO: Read-only 1 when the setting is read-only
1 H: Hidden 1 when the setting is hidden
2 DBL: 32-bit 1 when the following setting is a fractional value of this setting
3 RA: RAM-only 1 when the setting is not saved in nonvolatile memory
4 RR: Read-only
if running
1 when the setting is read-only if in running/operational state
5‘ P: Power Cycle
or Reset
1 when the setting change requires a power cycle or reset
60 Reserved
7 Extend Reserved to extend the descriptor table
Table E.22 60h Read Parameter Conversion Field Definition
Conversion
Value
Type Multiplier Divisor Offset Base
0Boolean 1101
1 Unsigned Integer 1 1 0 1
2 Unsigned Integer 1 10 0 1
3 Unsigned Integer 1 100 0 1
4 Unsigned Integer 1 1000 0 1
5 Hexidecimal 1 1 0 1
6 Integer 1 1 0 1
7 Integer 1 10 0 1
8 Integer 1 100 0 1
9 Integer 1 1000 0 1
10 Enumeration 1 1 0 1
11 Bit Enumeration 1 1 0 1
Table E.23 Responses to 60h Read Parameter Information Query Errors
Error Error Code Returned
Communication
Counter Increments
Illegal parameter to read Illegal Address (02h) Invalid Address
value
ParameterValue Offset+()Multiplier Base• •
Divisor
------ ----------------- ----------------- ----------------- ----------------- --------------------- ----------------- ------------=
value
value Divisor•
Multiplier Base•
------ ----------------- ----------------- ------ O f f s e t–=
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