D20/D200 Technical Overview
GE Information PRPI-019-3.00-10
2.4 I/O Peripheral Modules
The D20/D200 design is based on a distributed-processing architecture. As a result, the real-time
data acquisition and control software that interfaces with field points is installed on peripheral
modules, rather than on the main processor unit.
These I/O peripherals are intelligent modules that contain on-board microprocessors. They are
configured as slaves to the D20/D200 main processor. In this way, specific I/O processing is
distributed throughout the RTU to the appropriate I/O module.
D20 I/O peripherals communicate with the D20/D200 through a high speed, high-level data link
controller (D.20 Link) in the form of poll and response messages. The peripheral modules have a
serial communications port and a variable number of field connections.
The hardware construction of each module is similar (see Figure 18.) Each peripheral module
has common code stored in EPROM and a unique application configuration stored in RAM. The
base application code is stored on the D20/D200. At power up, the configuration and application
code are downloaded to the peripheral module from the D20/D200 main processor.
2.4.1 Types of I/O Peripherals
There are five basic types of I/O peripheral modules:
• D20S digital input
• D20A analog input
• D20K control output
• D20C combination input/output
• D20AC direct AC analog input
I/O peripheral modules are available with a variety of I/O point count support and termination
options. The following is a listing of the various D20 I/O peripherals that are currently available
from GE Grid Solutions:
Table 6 D20/D200 I/O Peripherals
Peripheral I/O Support Termination
D20A 32 analog inputs, standard version Compression
D20AD 32 analog inputs, standard version DB25
D20AX 32 analog inputs, standard version Disconnect
D20AB 32 analog inputs, standard version Barrier
D20AZ 32 analog inputs, high-voltage version Compression
D20S 64 digital inputs, standard version Compression
D20SD 64 digital inputs, standard version DB25
D20SX 64 digital inputs, standard version Disconnect
D20SB 64 digital inputs, standard version Barrier
D20SZ 64 digital inputs, high-voltage version Compression
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