When the port is closed, the TXD data line becomes Hi-Z state.

SuSh_1535366 · ‎Oct 22, 2018

Hello,

I am using CYUSB232 RDK to check the operation of CY7C65213-32LTXI.

After connecting the device to the USB, its TXD line is High.

However, once the port is opened / closed by software (ex. TeraTerm Pro), the TXD line becomes indeterminate(Probably Hi-Z state).

Therefore, incorrect data will be sent to the receiving side.

Is there a way to avoid this situation?

Thanks,

Shimamura

HirotakaT_91 · ‎Oct 28, 2018

Hi Shimamura-san,

Sorry for the delay in my response.

USB bus will enter idle mode if the COM port is closed and USB host can selective suspend the device after idle timeout.

This selective suspend will put the USB-UART device to deep sleep with Tx pin held Hi-Z mode.

Tx pin not in Hi-Z will violate USB specification VBUS current consumption limits.

Best regards,

Hirotaka Takayama

Re: When the port is closed, the TXD data line becomes Hi-Z state.