A8.10 Bumpless Transfer; A8.11 Setpoint Limiters; A8.11.1 When Pid Block Is In Auto Mode; A8.11.2 When Pid Block Is In Cas Or Rcas Mode - YOKOGAWA digitalYEWFLO Series User Manual

Mode Transitions
Transition
Destination Condition
Mode
1 O/S If O/S is set in MODE_ BLK.
target (or if O/S is set in
target inside the resource
block)
2 IMan If the specified condition is
met (read APPENDIX 8.14
"Initialization and Manual
Fallback (IMAN).")
3 LO If Track Enable is specified in
CONTROL_OPTS and the
value of TRK_IN_D is true
4 Man If Man is set in MODE_ BLK.
target or if IN.status (input
status) is Bad
5 Auto* If Auto is set in MODE_ BLK.
target
- AND -
if IN.status (input status) is
not Bad
6 Cas* ** If Cas is set in MODE_ BLK.
,
target
- AND -
if neither IN.status (input
status) nor CAS_IN.status
is Bad.
7 RCas* ** If RCas is set in MODE_
,
BLK.target
- AND -
if neither IN.status (input
status) nor RCAS_IN.status
is Bad.
8 ROut* ** If ROut is set in MODE_ BLK.
,
target
- AND -
if ROUT_IN.status (input
status) is not Bad
9 In accordance If RCAS_IN.status or
with the ROUT_ IN.status is Bad
SHED_OPT
(indicating a computer failure;
setting Read APPENDIX 8.17 "Mode
Shedding upon Computer
Failure" for details)
* To activate mode transitions to AUTO, CAS, RCAS, and
ROUT, the respective target modes must be set beforehand
to MODE_BLK.permitted.
** A transition to CAS, RCAS, or ROUT requires that
initialization of the cascade connection has been completed.

A8.10 Bumpless Transfer

Prevents a sudden change in the control output
NOT
OUT at changes in block mode (MODE_BLK) and
Conditions
at switching of the connection from the control
output OUT to the cascaded secondary function
block. The action to perform a bump less transfer
differs depending on the MODE_BLK values.
NOT if
condition 1 is

A8.11 Setpoint Limiters

met
Active setpoint limiters that limit the changes in the
NOT if either
SP value, differ depending on the block mode as
or both of
conditions 1
follows.
and 2 are met

A8.11.1 When PID Block is in AUTO Mode

NOT if any
one or more of
When the value of MODE_BLK is AUTO, the four
conditions 1 to
3 are met types of limiters are in force: high limit, low limit,
rate-of-increase limit, and rate-of-decrease limit.
NOT if any
one or more of
• Setpoint High/Low Limits
conditions 1 to
3 are met
• A value larger than the value of SP_HI_LIM
cannot be set for SP.
NOT if any
• A value smaller than the value of SP_LO_LIM
one or more of
conditions 1 to
cannot be set for SP.
3 are met
• Setpoint Rate Limits
The setpoint rate limits are used to restrict the
NOT if any
magnitude of changes in the SP value so as to
one or more of
conditions 1 to
change the SP value gradually towards a new
3 are met.
setpoint.
• An increase of the SP value at each execution
period (period of execution in the Block Header)
NOT if any
is limited to the value of SP_RATE_UP.
one or more of
conditions 1 to
• A decrease of the SP value at each execution
3 are met.
period (period of execution in the Block Header)
is limited to the value of SP_RATE_DOWN.
A8.11.2 When PID Block is in CAS or RCAS
By selecting Obey SP Limits if Cas or RCas
in CONTROL_OPTS (Read APPENDIX 8.13
"Measured-value Tracking"), the setpoint high/low
limits can be put into force also when the value of
MODE_BLK is CAS or RCAS.
<APPENDIX 8. PID BLOCK>
Mode
A8-6
IM 01F06F00-01EN