FAQ: What are some potential causes of an A.E2 alarm?
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An A.E2 alarm is a watchdog timer alarm, caused by either an MP940 processor time-out or an MP940-SGDH communications synchronization error. Below are some remedies.
1. Excessive system noise - Be sure that the MP940 is grounded to the SGDH (MP940 FG connection on power connector to the SGDH screw terminal on the front side of heat sink with a 16awg short ground wire), and the SGDH is connected directly to the field ground ground bar in the cabinet. Verify that the SGDH is properly grounded. Verify that the subpanel / ground terminal is properly grounded. Make sure that the machine is properly grounded to a sufficient building ground.
2. SGDH Comm Synch Error (Insufficient 24VDC power or bad wire connection)
1) Control power on SGDH and MP940 must power ON within 3 sec of each other
2) Check Dual Port Ram connection between SGDH and MP940
3) Check the 24VDC power supply capacity (if it dips below 21VDC for the unit will automatically watchdog trip as a safety precaution and generate an A.E2 alarm to indicate to user that there is a power supply issue). If the error occurs at the same point in the program all the time, chances are that the program is controlling an output point that draws more current than the power supply is capable of.
4) Verify that all terminal screws that bond wires are securly tightened, sometimes an intermittent connection in the power supply can be caused by loose wires after shipping or moving a machine (vibration of the machine may also cause screws to loosen).
3. MP940 Processor Time-Out - Typically caused when actual H or L scan 'time' exceeds H or L scan 'setting' respectively. The H scan will deterministically execute the entire H program/drawing and sub programs/drawings every H scan setting time cycle. Higher priority background tasks will interrupt the execution, but the H execution must occur in its entirety within the H scan setting. Otherwise, an error will occur. Any remaining time is left over to perform lower priority tasks. Likewise, the L scan will also deterministically execute the entire L program/drawing and sub programs/drawings every L scan setting time cycle. Higher priority tasks will interrupt its execution (such as the H scan), but the L execution must occur within the L scan setting. Otherwise, an error will occur. Hence, if too much time is spent in the H scan, the L scan will be starved of time!
As a program grows in size during development, and if this error occurs, most commonly the H scan time will need to be increased. In MW+, it will be necessary to perform a full compile/download for the new values to take effect and maintain after a power cycle.
Troubleshooting a Processor time-out - Verify that mProgram_HighScan_Current (SW00005, units of ms/100) and mProgram_HighScan_Maximum (SW00006, units of ms/100) does not exceed the High Scan setting (an MP940 Property attribute in MW+). Note that due to programming differences, various sections of code may not be run under certain conditions. Therefore, it will be necessary to test all conditions so that the maximum scan value can be determined.
Example: If mProgram_HighScan_Maximum starts to exceed 70 (0.7 ms) when the high scan setting is 1msec, it would be advisable to increase the high scan setting to 2msec or more as needed.
1) If that does not work, verify that mProgram_LowScan_Current (SW00011, units of ms/100) and mProgram_LowScan_Maximum (SW00012, units of ms/100) do not exceeded the Low scan setting).
2) Another method is prevention. Place critical tasks under high scan setting programs or drawings, and non-critical tasks under low scan programs or drawings. This logical separation also lends itself to good programming practices.
View our MP940/MW+ Program Template for an example by viewing FAQ # MMIR-5CM5LM
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Please read and understand the product instruction manual before installing, servicing or operating Yaskawa products. FAQ content and illustrations are provided as technical advice to augment the information in manual, not supersede it. It is not possible to give detailed instructions for all types of installation or support activities. The information described in the FAQs are subject to change without notice to improve the product or FAQ. Yaskawa assumes no responsibility for errors or omissions or damages resulting from the use of the information contained in any FAQ. All warnings, cautions and product instruction for product use must be followed. Installation, operation and maintenance should be carried out by qualified personnel. Failure to observe these and other precautions highlighted in the product manuals will expose the user to high voltages resulting in, serious injury or death. Qualified personnel are defined as individuals who are familiar with the installation, starting, operation and maintenance of Yaskawa products of the type described and have proper qualifications to perform the work.
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