How to use BOOTSEL ping as GPIO

Hello everyone,

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I use custom board with cyclonev chip.

I use BOOTSEL[2] and BOOTSEL[0] pings as GPIO28, 60 by bi-directional ping.

BOOTSEL[2] and [0] are pulled-up by 10k ohm and I can read ping level(high level) through GPIO_EXT_PORTA register.

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But I can't set LOW both ping with GPIO_SWPORTA_DR and DDR registers.

How should I set parameters to any registers ?

Or are thre any restriction to use BOOTSEL pings as GPIO output?