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Library Resources
The peripheral module library resources contain several general-purpose conversion routines.
2.4.4.2 Base-Application Code
There is base-application code for each type of peripheral module. Each base application
contains code for the following functions:
• Communication interface routines
• Diagnostics
• Application-specific maintenance
• Specific field input/output.
These functions are initiated by a separate clock source or hardware-driven IRQ rather than by
the real-time executive.
The base-application code is stored in the EPROM (labeled "pcommon") on the D20 main
processor and downloaded to the peripheral modules, where it is stored in RAM, along with a
checksum for verification purposes. A base-application database (unique to each peripheral type)
is downloaded to the peripherals at the same time. Peripheral base applications communicate
with the D20 main processor through the common code communications process, then over the
D.20 Link.
2.4.5 I/O Processing
D20 I/O peripherals provide specialized processing and storing/buffering functions for digital
inputs, analog inputs, control outputs, analog outputs, pulse accumulator inputs and
combinations of these, by gathering data from field sources or acting as an output unit to
interface with field devices.
I/O processing provides flexible, reliable, robust operation and is configurable on a per-point or
per-system basis. See Table 7. A detailed description of I/O processing is discussed in the
following sections in more detail for each module type.
Digital Output
Digital Input
Analog Input
GE Information
Table 7 I/O Processing
Type
•
Configurable control type, security and rules
•
Support simultaneous control of digital outputs
•
Request queuing
•
Request repetition
•
Software debouncing
•
Chatter filtering
•
Report limiting
•
Line noise filtering
•
Deadbanding
D20/D200 Technical Overview
Description
PRPI-019-3.00-10
43
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