DESCRIPTION AND OPERATION
MODES OF OPERATION
2 - 8
I-E96-117B
®
transfers to either normal mode or reverts back to bypass
mode as directed by the MFP module.
Normal Operation
Normal operation begins after the MFP module establishes
communication with the SAC station. In normal operation, the
set point, process variable, control output and analog inputs
appear on the appropriate bar graph on the SAC station face-
plate. The bar graph format is selected by setting the display
option dipswitches on the SAC station circuit board. In the
normal operation mode, the SAC station operates as a local,
manual/automatic basic or automatic cascade/ratio station.
Figure
shows a diagram of SAC station normal operating
modes. When the station loses communication with the MFP
module, it defaults to either the stand-alone mode or bypass
mode operation (if the auto bypass option is enabled).
Computer and Local Mode
A station may operate at one of two levels of process supervision
and control. The two levels are local and computer. The level of
the station defines whether the supervision and control of the
station is to be performed by a human operator via the SAC face-
plate controls or the equivalent station faceplate on a console
keyboard (local level) or by a supervisory computer program that
communicates with the station via a computer interface.
Figure 2-3. SAC Station Normal
Operating Modes
T00288A
NORMAL
OPERATION
MANUAL
BASIC
CASCADE
BASIC
RATIO
AUTOMATIC
