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GFK-0467K 1-1
Introduction
The Series 90-30, 90-20, and Micro PLCs are members of the GE Fanuc Series 90™ family of
Programmable Logic Controllers (PLCs). They are easy to install and configure, offer advanced
programming features, and are compatible with the Series 90-70 PLC.
The Series 90-20 PLC provides a cost-effective platform for low I/O count applications. The
primary objectives of the Series 90-20 PLC are as follows:
• To provide a small PLC that is easy to use, install, upgrade, and maintain.
• To provide a cost-effective family-compatible PLC.
• To provide easier system integration through standard communication hardware and protocols.
The Series 90 Micro PLC also provides a cost-effective platform for lower I/O count applications.
The primary objectives of the Micro PLC are the same as those for the Series 90-20. In addition,
the Micro offers the following:
• The Micro PLC has the CPU, power supply, inputs and outputs all built into one small device.
• Most models also have a high speed counter.
• Because the CPU, power supply, inputs and outputs all built into one device, it is very easy to
configure.
The software structure for the Series 90-30 PLC (except the 350 and higher models) and Series 90-
20 PLC uses an architecture that manages memory and execution priority in the 80188
microprocessor. The 350 and 360 series of 90-30 PLCs use an 80386EX microprocessor. The
Series 90 Micro PLC uses the H8 microprocessor. This operation supports both program execution
and basic housekeeping tasks such as diagnostic routines, input/output scanners, and alarm
processing. The system software also contains routines to communicate with the programmer.
These routines provide for the upload and download of application programs, return of status
information, and control of the PLC.
In the Series 90-30 PLC, the application (user logic) program that controls the end process to which
the PLC is applied is controlled by a dedicated Instruction Sequencer Coprocessor (ISCP). The
ISCP is implemented in hardware in the Model 313 and higher and in software in the Model 311
systems, and the Micro PLC. The 80188 microprocessor and the ISCP can execute simultaneously,
allowing the microprocessor to service communications while the ISCP is executing the bulk of the
application program; however, the microprocessor must execute the non-boolean function blocks.
Faults occur in the Series 90-30 PLC, Series 90-20 PLC, and the Micro PLC when certain failures
or conditions happen that affect the operation and performance of the system. These conditions
may affect the ability of the PLC to control a machine or process. Other conditions may only act as
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