Early Power Estimator for Intel® Arria® 10 FPGAs User Guide

ID 683688
Date 9/27/2022
Document Table of Contents

3.5. Early Power Estimator Input Field Dependencies

The value you specify for some input fields may affect the allowed values for other fields.

For example, the device package that you select may determine what transceiver grades are selectable. If you change the selected device package, and the currently selected transceiver grade is still legal for the new package, the Transceiver Grade value does not change. However, if the currently selected transceiver grade is not compatible with the selected device package, the Transceiver Grade value automatically change to one of the legal values.

Changes that you make in one worksheet may affect values on another worksheet, because of dependencies between input fields. For example, if you select a device that does not support the current I/O standard specified in the I/O worksheet, that I/O standard will automatically change to one that is supported by the new device.

In general, the Early Power Estimator for Arria® 10 does not automatically change an input value unless it is necessary to preserve the legality of the input. Changes in one field have minimal impact on other fields, while ensuring that overall combination of field values are legal. However, this can sometimes lead to unanticipated results. Consider the following example:

Assume that Dev1 is selected in the Main worksheet, and I/O standard IO1 is selected in the I/O worksheet. Assume also that device Dev1 supports I/O standards IO1 and IO2. Suppose that you change the device selection to Dev2, which supports only one I/O standard, IO2. As a result of you changing the device selection, the I/O standard in the I/O worksheet will change to IO2. If you then reverted the device selection back to Dev1, the I/O standard would not change, because IO2 is a legal I/O standard value for the device Dev1. The important point to note, is that the changing of device from Dev1 to Dev2 and back again, had the—potentially unintended—consequence of changing the I/O standard in the I/O worksheet.

Note: In most cases, field dependencies are limited to the same worksheet, and often even within the same row. However, device, device grade, package and transceiver grade selection can have a much wider impact, as illustrated above. A simple way to verify that no unintended changes resulted from changing a device is to use the Export CSV function to export the EPE state before and after the change in device selection. You can then compare the two CSV files using a third-party diff utility to identify any fields that have changed.