National Instruments NI-FBUS - Manual (Page 73)

Chapter 4 Parameters
NI-FBUS Configurator User Manual 4-8 ni.com
Mode Shedding Parameters
Mode shedding parameters handle communication failures with a host.
For remote modes in which the cascade input is periodically written by a
host application, Foundation Fieldbus provides mode shedding to handle
failure of the host application. For the
RCas mode and ROut modes, there
are two timeout parameters in the resource block: SHED_RCAS and
SHED_ROUT . If the block is in a remote mode and the block input being used
( RCAS_IN or ROUT_IN ) is not updated within the timeout period, the block
sheds to a higher priority mode. The action taken by the block when mode
shedding occurs is defined by the
SHED_OPT parameter, as described in the
table below. The shed condition ends when the host writes the remote input
parameter. If a normal return shed option is selected, the block attempts to
enter the original remote mode. If a no return shed option is selected, the
target mode is changed at the time the block sheds mode, and the block does
not attempt to enter the original lower priority mode when the shed
condition ends.
Option Parameters
Table 4-6. Mode Shedding Parameters
RCAS_IN SHED_OPT
RCAS_IN_D SHED_RCAS
ROUT_IN SHED_ROUT
Table 4-7. Option Parameters
CLR_FSTATE SET_FSTATE
CONTROL_OPTS SHED_OPT
FAULT_STATE SIMULATE
FEATURE_SEL/FEATURES SIMULATE_D
FSTATE_TIME SP_HI_LIM
FSTATE_VAL SP_LO_LIM
FSTATE_VAL_D SP_RATE_DN
GRANT_DENY SP_RATE_UP