VCU108 schematics- USB-UART interface

[jayaskr]

The schematics for USB-UART interface on Page 61 show the component NDS331N at the TxD, RxD, CTS and RTS  terminals of CP2105. What is the function of the device NDS331 in this context. Is it required by the UART-lite core to be implemented on Virtex Ultrascale device? These devces are not provided in the KC705 board, where the device CP2103 is used. How are CP2103 and CP2105 UART interfaces different (except that  CP2105 has dual interface).

Regards.

--Jaya

[htsvn]

hi,

looking at the schematic, it does not look to be related to implementing the controller of uart. let me check the reason for this and get back.

--hs

[jayaskr]

Hi,

I have looked at schematics of KCU105, KC705, VCU108, VCU110, VCU118 and have observed the following.

1.  In KC705 board, VIO pin of CP2103 is powered by 2.5V and TX, RX signals are mapped to 2.5V I/O bank of FPGA , the external MOSFETS are not used.

2. In the boards that use Ultrascale devices, VIO of CP2105 is powered by 1.8V ,external MOSFETS are used and the corresponding Tx,Rx signals are mapped to 1.8V IO banks on the FPGA. Has this  got to do with detection of logic levels at 1.8V I/Os on both ends?

 Can VIO of CP2105 be powered to 3.3V and the TX, Rx signals be mapped to a 3.3V banks without the use of external MOSFET devices?

Regards.

--jaya