E.14
SEL-787 Relay
Instruction Manual
Date Code 20081022
Modbus RTU Communications
Communications Protocol
The Parameter Descriptor field is defined in
.
The Parameter Conversion field is defined in
.
to calculate the actual (not scaled) value of the parameter
(setting):
Equation E.1
to calculate the scaled setting value:
Equation E.2
The relay response to errors in the query are shown
.
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
6
0
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
0
Boolean
1
1
0
1
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
•
----------------------------------------------
Offset
–
=
Summary of Contents for SEL-787
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