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Not only must you be able to move your material to the proper location, but you need to send the proper signals to the receiving device to ensure proper transfer of material.

This is where SEMI E84 comes into play.

When looking at automated material handling systems (AMHS), it is important to know that SEMI E84 is a carrier handoff communication specification. It does not specify distance measurement tolerances. When using Hokuyo’s DMS, DMG, or DMJ products in your SEMI E84 applications, you are transmitting data optically and enabling communication.

Knowing this will allow you to better understand what you are looking for in your interface and troubleshoot issues when they occur.

What Does SEMI E84 Specify?

SEMI E84 is designed to provide enhanced parallel I/O interface specifications between active equipment, such as transport systems, and passive equipment, such as process tools and stockers.

The specifications published by SEMI E84 cover the following:

  • Signal definitions.

  • Load port selection signals.

  • Transfer sequences and timing diagrams.

  • Error handling provisions.

  • Connector and pinout information.

  • Interface unit dimensions for corresponding load ports.

Use the applicable licensed edition of SEMI E84 and your equipment supplier’s documentation to meet the specified requirements.

Ensuring Proper Communication During Handoff

Your transport has arrived at the destination process tool. Several things must work together to ensure that your process tool and transport hand off correctly. Not only do you need to reach that destination, but both devices need to communicate with one another through the handoff interface.

An optical link transmits these interface signals from one end to the other. An additional distance sensor may send information to your process equipment, but it serves a different purpose.

Three Things to Consider When Designing Your System

  • Positioning: Can my equipment get to the desired position and stay there?

  • Optical communication: Can my transmitter and receiver communicate during handoff?

  • Controller behavior: Will my controllers do what they are supposed to?

Any of these issues can cause your handoff to fail. Simply replacing a distance sensor may not solve all of your communication problems, and installing a SEMI E84 compatible product does not ensure that the complete AMHS works correctly.

Troubleshooting Your AMHS Handoff

Here are some things to check when your AMHS is having trouble handing off carriers.

Distance and Obstruction Issues

Make sure that your optical heads can see each other at all positions where your equipment can dock. Bracket movement, improper installation, or an obstruction may affect the communication path.

Check Communication Distance and Alignment

Review the specifications of the product you have installed and check whether your setup meets its communication distance and alignment requirements. Communication distance describes how far apart the optical heads can operate. It is not a distance measurement output.

Wrong Model or Wiring

Just because your connectors fit does not mean that they are configured the same way. Double-check your model number, suffix, pinout, and electrical specifications to make sure they are compatible with your equipment.

Hokuyo’s DMS Series for SEMI E84 offers different configurations for active and passive systems.

Handshake and Timing Issues

Just because your link can communicate does not mean that your handshake will work. Controllers may not be reading inputs properly, or your equipment may be sending unexpected signals.

Record and Compare the Signal Sequence

Record the signals being sent and received at both ends of your interface. Compare them with your required sequence and determine what went wrong first.

Troubleshooting Problems That Are Hard to Find

Sometimes an issue happens only occasionally, making it difficult to diagnose. Have a plan for recording your communications when you install your system.

Hokuyo’s DMG Series allows you to log handoff signals. This can help you diagnose communication problems.

Tolerances for Fab Applications

Do not assume that all applications in a semiconductor fab simply require a more accurate distance sensor.

Your SEMI E84 optical interface must operate within the selected device’s specifications. Make sure that communication distance, alignment, and other installation factors are taken into account.

Other factors, such as carrier positioning and clean environment requirements, should also be checked when designing your system. However, these are not distance measurement tolerances specified by SEMI E84.

Test your transfer at the various positions your equipment will encounter, and simulate failed transfers to evaluate the system’s recovery behavior.

How Does Hokuyo’s DMS Series Help?

The DMS Series for SEMI E84 is designed to transmit interface data optically. Hokuyo describes these products as supporting an 8-bit optical handshake with a 25-pin D-sub connector. Check your application requirements and the exact model configuration to determine which DMS product will work for your needs.

If you want to log your handshake information, Hokuyo also offers the DMG Series. DMJ products are also available within Hokuyo’s optical data transmission lineup for SEMI E84 applications.

These products support the communication interface in your SEMI E84 application, but you should still verify that your overall system meets the applicable requirements.

Questions to Ask Before Choosing Your Interface

  • Which SEMI E84 edition are you trying to meet? Are there customer specifications you need to comply with?

  • Is your equipment active or passive?

  • Do your connectors match? What about the pinout and electrical specifications?

  • Is the separation within the device’s communication range? What alignment variation must it accommodate?

  • Could anything block or interfere with communication?

  • Will your controllers execute the proper handshake?

  • What logging will be available when a problem occurs?

  • How will you test failed handoffs and recovery behavior?

  • What other sensing do you need?

Use these questions to guide your interface selection. There are many factors to consider when moving carriers around your fab.

Explore Hokuyo’s Optical Communication Products

Learn more about our optical data transmission products, or check out the Hokuyo Product Guide for more information.

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