弱问：关于VREF

dalewu

看Cyclone II的一个handbook,里面有这么一句
If a bank uses a voltage-referenced I/O standard, then these pins are used as the voltage-reference pins for the bank. If voltage reference I/O standards are not used in the bank, the VREF pins are available as user I/O pins.
问题是怎么判断一个bank有没有使用voltage-referenced I/O standard？

sycall

it depends on what kind of interface you choose to implement in this bank. For example, if you want to implement a DDR interface, you should use VREF as a reference voltage.