ABB 615 Series ANSI, Manual

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Section 3
1MAC052634-MB D
Vendor-specific implementation
24 615/620 series ANSI
Communication Protocol Manual
Control structure register assembling order
The Modbus client can assemble all the control structure registers and write them in one
multiple registers write function 16 request.
The Modbus client can also write the registers in several separate transactions or even one
by one using registers write function 06. The execute register has to be written last and no
more than 15 seconds may elapse between the separate register writes. The control
structure operation will time out after 15 seconds after the last register write. The timeout
between select and operate steps is fixed to 15 seconds regardless of the controllable
object’s configured timeout value.
Exception codes
Only a few exception code alternatives exist for control structures:
• 01 = illegal function
• 02 = illegal address
• 03 = illegal value
The exception code 03 is also returned if a command operation is rejected due to the IED's
other internal reasons. The client can find the code for the internal rejecting reason in the
SSR6 register.
For example. the primary internal rejection reasons for control structure write operations
may be that:
• The Modbus control structure write has timed out (15 sec).
• The client has no write authority.
• The IED is in the local state.
• The control operation is blocked, that means already reserved, by another client.
If a positive acknowledgement is returned, the control command has been initiated inside
the IED.
3.3.6.3 Additional control operations
Secured and unsecured control operations
If the control command initiates an object that is internally defined to perform a secured
control operation, the SSR6 register CmdState bits will show “Command In Progress”
during the actual control operation. Once the command sequence is over, the SSR6
command state bits change to “Response Ready”. The contents of the SSR6
CmdResultCode can then be examined.
In unsecured operation mode, the positive confirmation response to a Modbus command
request is based on the internal, IEC 61850 level, positive activation confirmation and not
If several clients are allowed to perform control operations simultaneously,
this method should not be used by more than one of the multiple clients in
question.