Specifications

ST900 Family General Handbook
667/HB/32900/000 Issue 11 Page 145 of 265
Under Option 2, all stages are demand and extension dependent. A stage change
will not occur unless there are no extensions for the current stage or the ‘F’ bit is
lifted and there is a demand for the next stage with or without an ‘F’ bit. (TCD 316)
15.7 Method of Plan Introduction
Certain contracts require that the controller must synchronise with the Plan quickly.
To achieve this, the following constraints are placed on the UTC facility:
The Stage movement restraints table used by UTC should not have purely
prohibited moves or Ignore moves configured. They should either be allowed moves
or, if this is not acceptable for safety reasons, alternative moves should be
specified. If alternatives are specified, it is preferable for the alternative stage to be
one or two stages ahead in cyclic order of the original target stage, for example:
If the move 1-2 is not to be allowed,
Then the alternative could be 1-3 or 1-4.
15.8 Special UTC Requirements
Special UTC requirements that can be programmed using special conditioning may
include (but are not limited to) the following:
a) One ‘G’ bit for more than one stage. Normally the ‘G’ bit does not stay
active during the interstage between the stages. If this is required, a
dummy phase is allocated to all the stages that are to return the ‘G’ bit.
The dummy phase will then remain active during the interstage and is
programmed to return the ‘G’ bit instead of the stages active.
b) UTC mode active disables selection of VA or Fixed Time mode.
c) Fixed Time mode or Manual mode active returns ‘G1/G2’ and the current
‘G’ bit.
d) Special stage change conditions.
15.9 OTU Links
The OTU in the Siemens Type 900 Controller may also control and monitor an
adjacent controller over a cabled link.