NEC FC-9801X Industrial Computer

2.3 Extended Storage Options

The FC-9801X allows for the installation of a second drive inside the body, which can be a 5-inch or 3.5-inch floppy disk drive. In addition, through the external file extension unit (FC-9813), up to:

Two 5-inch or 3.5-inch floppy disk drives;

A 5-inch hard drive (10 MB or 20 MB, compatible with PC-9801-27 interface board).

This hierarchical storage architecture enables system integrators to flexibly configure according to project requirements: running real-time tasks with RAM files, distributing and backing up programs with floppy disks, storing historical data with hard disks, and each performing their own duties.

Scalability and chassis design

3.1 Built in five expansion slots

FA/LA systems often require the connection of multiple specialized interfaces: A/D, D/A conversion cards, digital I/O cards, serial communication cards (RS-232C/422/485), GPIB, fieldbus (such as FL net), or motion control cards. The FC-9801X provides 5 expansion slots directly inside the chassis, which can accommodate most of the required cards for applications without the need for an external expansion chassis. This design significantly reduces the physical volume and connection cables of the system, improving the overall reliability of the machine.

3.2 19 inch rack installation and dust prevention measures

To accommodate standard industrial cabinets, the FC-9801X standard comes with a 19 inch rack mounting mechanism according to JIS specifications. Users can install it together with other PLCs, frequency converters, power modules, and other equipment in the control cabinet, significantly improving space utilization.

In terms of dust prevention, in addition to the optional simple dust filter set (FC-9893) directly installed at the air inlet of the host, the whole machine can also be installed into a commercially available sealed dust rack, suitable for high dust environments such as cement, textile, and food processing. These details reflect NEC's profound understanding of practical issues in industrial sites.

3.3 Rich back interface

From the schematic diagram of the back panel in the product information, it can be seen that FC-9801X provides the following standard interfaces:

AC power input and output (used for connecting external devices such as displays in series)

RAS terminal block (centralized connection of alarm input and output signals)

Mouse interface (which was still advanced at that time)

1 MB type floppy drive interface/640 KB commercial floppy drive interface (compatible with different media formats)

RS-232C serial port (used for PLC programming, modem communication, etc.)

Printer parallel port

Monochrome display interface

Digital RGB interface

Simulate RGB interface (can directly connect to various industrial displays)

The diversity of this interface allows the FC-9801X to directly replace dedicated controllers in older systems without the need for additional protocol converters.

RAS Function: Systematic Implementation of Reliability, Availability, and Serviceability

RAS "stands for Reliability, Availability, and Serviceability. FC-9801X elevates RAS functionality from simple power monitoring to a system level anomaly detection and management framework, including:

4.1 Power Failure Detection and Watchdog Timer

Power outage detection: When the AC input voltage drops below the threshold, the system immediately generates an NMI interrupt, notifying the application to perform emergency data saving, output safety status, and other operations before allowing the CPU to stop working. This avoids data damage or actuator uncertainty caused by sudden power outages.

Watchdog timer: The user program must periodically reset the watchdog. If the software gets stuck in a dead loop or task blockage, the watchdog timeout will trigger a hardware reset or interrupt, automatically restoring system operation. This feature is particularly important for unmanned remote stations.

4.2 Temperature rise detection and memory refresh check

Temperature detection: There is a temperature sensor inside the chassis. When the ambient temperature rises abnormally (such as cabinet fan failure or high summer temperatures), the system can issue an alarm contact signal or send an interrupt to the CPU to remind the operator to take measures to prevent component overheating and failure.

Memory refresh check and parity check: Regularly verify the normal operation of the DRAM refresh circuit and check critical memory areas to detect early signs of hardware aging.

4.3 External alarm input and remote reset

External alarm input: The alarm contacts of on-site devices (such as motor thermal overload relays, pressure switches) can be directly connected to the RAS terminal block. When an external alarm occurs, the system can generate an interrupt, triggering the corresponding safety interlock program. This enables FC-9801X to not only serve as a computing platform, but also as a monitoring node in the security chain.

Remote reset: The CPU can be hardware reset through external contacts or remote communication commands. In distributed systems, administrators can restore crashed controllers without physically visiting the site, significantly improving system availability.