How to Address and Configure IC693CHS397 Main Baseplate with IC693CHS398 Expansion Racks in GE Fanuc Series 90-30 PLC Systems
Industrial automation professionals often work with legacy GE Fanuc Series 90-30 PLC platforms. The IC693CHS397 main baseplate and IC693CHS398 expansion baseplate form a reliable combination for factory automation. However, engineers must understand rack addressing clearly. This guide explains the configuration logic, cable limits, and power budgeting. It also offers practical insights for control systems integrators.
Main Rack vs. Expansion Rack: A Clear Architectural Split
The Series 90-30 system allows only one CPU baseplate. The IC693CHS397 serves as that unique main rack. It holds the CPU in Slot 1 and provides four extra I/O slots. In contrast, the IC693CHS398 acts as an expansion rack. It offers five I/O slots but no CPU slot. Therefore, the main rack always defaults to Rack Number 0. Hardware design fixes this assignment. As a result, you cannot change the main rack number.
No Physical Jumpers on the IC693CHS398: Software Takes Control
Many engineers expect DIP switches or jumpers for rack addressing. However, the IC693CHS398 does not use physical settings. Instead, you assign the rack address through software. Proficy Machine Edition or Logicmaster 90-30 handles this task. The CPU then recognizes each expansion baseplate by its logical position. Consequently, no manual jumper changes are needed on the hardware itself. This design simplifies installation and reduces human error.
Software-Based Rack ID Assignment and I/O Addressing
The CPU identifies each expansion rack by a Rack ID number. This number ranges from 1 to 7. You set this ID during hardware configuration. The software links each physical rack to a specific Rack ID. As a result, the CPU addresses I/O modules based on this logical assignment. For example, an input module in Slot 1 of Rack ID 1 gets a unique %I memory address. The physical daisy-chain position does not determine the Rack ID. Only the software configuration does.
Maximum Expansion Capacity Depends on CPU Model
The number of supported expansion racks varies by CPU model. Older CPUs like the 331, 340, and 341 support up to four expansion racks. Newer CPUs, such as the 350 series and above, support up to seven. Moreover, each IC693CHS398 rack provides five slots. Therefore, a fully populated seven-rack system offers 35 additional I/O slots. However, you must also check power supply limits. The CPU rack power supply must handle the cumulative load of all expansion racks.
Cable Length Limits and Physical Layer Rules
A 25-pin D-type expansion cable connects the racks. The maximum cumulative cable length is 50 feet (15 meters). This limit applies to the entire daisy chain. Consequently, you must calculate the total length from the CPU rack through all intermediate racks. Exceeding this limit causes communication errors. Furthermore, daisy-chaining requires careful routing. The OUT port of one expansion rack connects to the IN port of the next. This creates a sequential bus topology. In my experience, keeping cables short and away from high-voltage wiring improves reliability.
Power Budgeting for Reliable Expansion Rack Operation
Each IC693CHS398 expansion rack needs its own power supply module. The backplane alone consumes 170 mA at 5 VDC. However, this figure excludes the power demands of installed I/O modules. Discrete input modules typically draw 100–150 mA each. Analog modules may draw 300–500 mA each. Therefore, the CPU rack power supply must have enough capacity. A typical CPU power supply provides 5 A at 5 VDC. As a result, you must calculate the total load. Failure to do so leads to intermittent rack failures. I always recommend adding a 20–30% margin for future expansion.
Practical Configuration Workflow for Engineers
Follow this logical sequence for a smooth setup. First, install the IC693CHS397 main rack. Second, insert the power supply and CPU modules. Third, connect the IC693CHS398 expansion racks with expansion cables. Fourth, launch your PLC programming software. Fifth, add each expansion rack to the hardware configuration. Sixth, assign a unique Rack ID (1 through 7) to each rack. Finally, configure the I/O modules within each rack. This workflow ensures proper I/O addressing and system functionality.
Author Insights and Industry Commentary
Legacy PLC systems like the Series 90-30 remain widespread in industrial automation. Many factories still rely on them for control systems and DCS integration. However, spare parts and expertise are becoming scarce. Therefore, I advise engineers to document rack addressing carefully. A clear configuration table saves hours during troubleshooting. Moreover, consider migrating to newer platforms when possible. Yet for existing installations, the IC693CHS397 and IC693CHS398 pair still delivers solid performance. Proper power budgeting and cable management are the keys to long-term reliability.
Application Case: Expanding a Packaging Line
A food packaging plant needed more I/O points for a new labeling station. The existing Series 90-30 system used an IC693CHS397 main rack. The engineer added two IC693CHS398 expansion racks. They assigned Rack IDs 1 and 2 in Proficy Machine Edition. The total cable length stayed under 30 feet. Power calculations showed a 40% margin on the CPU supply. As a result, the expansion ran without errors for over two years. This case shows how software-based addressing simplifies factory automation upgrades.
Frequently Asked Questions (FAQ)
Q1: Can I change the Rack Number of the IC693CHS397 main baseplate?
No. The main rack is fixed as Rack Number 0 by hardware design. You cannot reassign it to a different number.
Q2: Does the IC693CHS398 expansion rack require physical jumpers for addressing?
No. The IC693CHS398 uses software-based Rack ID assignment. You configure the Rack ID in Proficy Machine Edition or Logicmaster 90-30.
Q3: What is the maximum number of expansion racks I can add?
It depends on the CPU model. Older CPUs (331, 340, 341) support up to four expansion racks. Newer CPUs (350 series and above) support up to seven.
Q4: What is the maximum cable length for the expansion bus?
The cumulative cable length for the entire daisy chain must not exceed 50 feet (15 meters).
Q5: How do I calculate power needs for expansion racks?
Add the backplane consumption (170 mA at 5 VDC per rack) plus the current draw of all installed I/O modules. Ensure the CPU power supply has at least 20–30% spare capacity.
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