I'm considering using GPO of AD9364 in auto-toggle (ENSM control) for T/R switch as stated in the UG-673 reference manual. I searched for reference materials but found few as boards like FMCOMMS4 do not use T/R switches and those that do like the Ettus/NI B200 use BBP/FPGA ports for T/R control. So I have a few inquiries:
1) The RM says to initialize GPO using Reg 0x27 and select which GPOs to toggle using Reg 0x20 when the transceiver enters Rx or Tx states. However, it is unclear what happens when it exits said states. Does it toggle back to default state during entry to Alert state? Or does it hold the current GPO state until next entry to Rx or Tx state? I'm assuming it is the former.
2) What happens when Reg 0x27 is reinitialized? For example, when ENSM is currently in Rx or Tx, and Reg 0x27 is written to, will the GPOs be affected immediately? Is there an established/safe way to reinitialize the default (alert) state of the GPOs?
3) What happens to the GPO when set to ENSM control but the device is in FDD mode?
4) Table 50 of UG-673 shows writing Reg 0x20 with 0x10, meaning toggle a single bit (GPO_0) in Rx mode according to the register definition. But Figure 54 shows both GPO_0 and GPO_1 toggling, which thus leads to my confusion as to how GPO auto-toggles.
Thanks for any clarification.