You may receive an error message “Can’t access JTAG chain” when you configure Cyclone® III and Cyclone IV E devices in an EQFP E144 package. This is because all E144 packages have an exposed pad at the bottom of the package. This exposed pad represents the ground pad that must be connected to the ground plane on your PCB. This exposed pad is used for electrical connectivity and not for thermal purposes. Failing to solder the exposed pad to ground will cause the device to hold in a reset state and all types of configuration modes will fail.
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