9.1.2.3
Dataflow from PSCA to Controller
Dataflow from the PSCA to the Mark VIe controller is of two types: fixed I/O and Modbus I/O. Fixed I/O is associated with
the smart pressure transducers and the Kollmorgen
®
electric drive data. This data is completely processed every frame, the
same as conventional I/O. These signals are mapped into signal space, have individual health bits, and have offset/gain
scaling. Several of these signals are configured to support system limit checking.
Modbus
: Modbus I/O is the I/O associated with the Modbus ports. Because of the quantity of these signals, they are not
completely processed every frame; instead they are packaged and transferred to the Mark VIe controller, over the IONet
through a special service. This can accommodate up to 2400 bytes, at 4 Hz, or 9600 bytes at 1 Hz, or combinations thereof.
This I/O is known as second class I/O, where coherency is at the signal level only, not at the device or board level. Health bits
are assigned to individual points in the same fashion as the other protocols, and system limit checking is not performed. Three
consecutive time-outs are required before a signal is declared unhealthy. Diagnostic messages are used to annunciate all
communication problems. The input value is cleared for a given signal after four consecutive time-outs occur on that signal.
Honeywell
®
Pressure Transducers
: Serial ports 1 and 2 support the Honeywell pressure configuration. It reads inputs from
the Honeywell Smart Pressure Transducers, type LG-1237. As an option (pressure transducers or Modbus) this service is
available only on ports 1 and 2. The pressure transducer protocol utilizes interface board DS200XDSAG#AC, and RS-422.
Each port can service up to six transducers. The service is 375 kbaud, asynchronous, nine data bits, (11 bits including start
and stop). It includes communication miss counters, one per device, and associated diagnostics as failsafe features.
After four consecutive misses, it forces the input pressure to 1.0 psi, and posts a diagnostic. After four consecutive hits (good
values) it removes the forcing and the diagnostic.
Kollmorgen Electric Drive
: Three ports (any three, but no more than three) support the Kollmorgen electric drive. It
communicates with a Kollmorgen Electric Fast Drive FD170/8R2-004 at a 19200 baud rate, point-to-point, using RS-422.
PSCA Modbus Master (Serial Communication) Module
GEH-6855_Vol_II System Guide 287
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