Intel® FPGA Power and Thermal Calculator User Guide

ID 683445
Date 12/13/2021
Public

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3.2.3. Intel® FPGA PTC 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 changes to one of the legal values.

Changes that you make on one page may affect values on another page 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 page, that I/O standard automatically changes to one of the I/O standards supported by the new device.

In general, the Intel® FPGA Power and Thermal Calculator ( Intel® FPGA PTC) 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 page, and I/O standard IO1 is selected in the I/O page. 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 page changes to IO2. If you then reverted the device selection back to Dev1, the I/O standard does 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 page.

Note: In most cases, field dependencies are limited to the same page, 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 File > Save As function to export the Intel® FPGA PTC state before and after the change in device selection. You can then compare the two .ptc files using a third-party diff utility to identify any fields that have changed.

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