Yokogawa YVP110 - Manual (Page 85)

<16. PID Function Block>
16-4
IM 21B04C01-01E
16.13 Initialization and Manual
Fallback (IMan)
Initialization and manual fallback denotes a set of
abnormality handling actions in which a PID block
changes mode to IMan (initialization manual) and
suspends the control action. Initialization and
manual fallback takes place only when the following
condition is met:
• The quality component of BKCAL_IN.status
(data status of BKCAL_IN) is Bad.
- OR -
• The quality component of BKCAL_IN.status is
Good (c)
- AND -
The sub-status component of BKCAL_IN.status
is FSA, LO, NI, or IR.
16.14 Manual Fallback
Manual fallback denotes an abnormality handling
action in which a PID block changes mode to Man
(manual) and suspends the control action.
The manual fallback action is enabled to take place
if the Target to Manual if BAD IN option in STATUS_
OPTS is set as true, and it takes place when the
following condition is met:
• IN.status (data status of IN) is Bad except when
the control action bypass is on.
16.14.1 STATUS_OPTS
The table below shows the options in STATUS_
OPTS.
Table 16.4 STATUS_OPTS of PID Block
Bit
Options in
STATUS_
OPTS
Description
0 IFS if BAD IN Sets the sub-status component
of OUT.status to IFS if IN.status
is Bad except when PID control
bypass is on.
1 IFS if BAD
CAS IN
Sets the sub-status component of
OUT.status to IFS if CAS_IN.status
is Bad.
2 Use Uncertain
as Good
Does not regard IN as being in Bad
status when IN.status is Uncertain
(to prevent mode transitions
from being affected when it is
Uncertain).
5 Target to
Manual if BAD
IN
Automatically changes the value of
MODE_BLK.target to Man when IN
falls to Bad status.
9 Target to next
permitted
mode if BAD
CAS IN
Automatically changes the value
of MODE_BLK.target to Auto (or to
Man if Auto is not set in Permitted)
when CAS_IN falls to Bad status.
16.15 Auto Fallback
Auto fallback denotes an action in which a PID
block changes mode from Cas to Auto and
continues automatic PID control with the user-set
setpoint. To enable the auto fallback action to take
place:
• The Target to next permitted mode if BAD CAS
IN option must be preset to true in STATUS_
OPTS.
- AND -
• Auto must be preset in MODE_BLK.permitted.
If the above settings are made, auto fallback
takes place automatically when the following
condition is met:
• CAS_IN.status (data status of cascade
setpoint) is Bad except when the control action
bypass is on.
16.16 Mode Shedding upon
Computer Failure
When (1) the data status of RCAS_IN, which is the
setting received from a computer as the setpoint
SP, falls to Bad while the PID block is running in the
RCas (remote cascade) mode, or when (2) the data
status of ROUT_IN, which is the setting received
from a computer as the remote output signal, falls
to Bad while the PID block is running in the ROut
(remote output) mode; mode shedding occurs in
accordance with the SHED_OPT setting.