ADS7950: GPIO output configuration problem

Part Number: ADS7950

Hi team,

According to ADS7950 datasheet, 4 GPIO pins can be configured as general purpose I or O. But the customer writes 0x400c to the register (GPIO3 is configured as output); then writes 0x1818 to the register (Manual Mode + GPIO3 output is 1), the ADS7950 has no response. What reason is this? Could you give some advice?

Best Regards,
Amy Luo