While researching for chips to interface with the 65xx family of CPUs, I found that FTDI has several chips that converts between USB and UART, or parallel.

And it seems to me that it would make it possible to interface the veteran chip with the myriad of USB devices across the world, of course, through the use of PIAs, VIAs, ACIAs, or certain universal UART chips I've also found from several manufacturers.

What do you think?

FT230X – Full Speed USB to Basic UART
FT231X – Full Speed USB to Full Handshake UART
FT234XD – Full Speed USB to Basic UART
FT240X – Full Speed USB to 8- bit FIFO

Important detail: are these USB host devices or slaves? USB is not symmetric in the way RS-232 is.

They look like they're all slaves, as far as USB is concerned.

FT230X, FT231X, FT234XD and FT240X are USB slaves.

Vinculum can work as a host or slave.
Vinculum can handle a USB mouse. //The firmware manual doesn't mention USB keyboards, but there is an appnote for interfacing a HP DeskJet 460 USB printer.
Vinculum is supposed to be able to handle 4GB USB sticks (haven't tried bigger USB sticks), but it only can open one file at a time, and the firmware doesn't support long filenames in FAT32.
Hmm... some years ago, when we had tinkered with a VDIP2 at work, IIRC the 'seek' command somehow only had worked for the first 64kB of a file, you better check this.

Some years ago we also had tried the Vinculum 2 at work (which is completely different from the Vinculum),
but we were not happy with the toolchain so the eval board had ended up in the trash can.

The W65C265SXB (and probably the W65C134) use a FT232RL USB to serial connected to one of the built in UARTSs.
The W65C816SXB (and probably the W65C02SXB) use FT245RL USB to FIFO connected to a VIA that also bit bangs the control signals.

_________________
Andrew Jacobs
6502 & PIC Stuff - http://www.obelisk.me.uk/
Cross-Platform 6502/65C02/65816 Macro Assembler - http://www.obelisk.me.uk/dev65/
Open Source Projects - https://github.com/andrew-jacobs

Thanks. USB slave, then... so... what about these ones? They they are targeted to be managed with Android, but by looking at the datasheet, there is an UART end there... What am I missing?

FT311D – Host

• USB 2.0 Full Speed Host
• Hardware selectable interfaces - GPIO, UART, PWM, I2C Master, SPI Slave or SPI Master.
• USB ERROR indicator pin.
• Single power supply operation at 3.3V.
• Internal 1.8V LDO regulator.
• Internal memory for storing configurable strings – allows Android to automatically detect the device and application.
• Extended operating temperature range : -40°C to 85°C.
• Available in Pb-free QFN-32 and LQFP-32 packages (RoHS compliant).

FT312D – USB Host Chip

• USB 2.0 Full Speed Host
• USB to UART bridge
• USB ERROR indicator pin
• Single power supply operation at 3.3V
• Internal 1.8V LDO regulator
• Internal memory for storing configurable strings – allows Android to automatically detect the device and application
• Extended operating temperature range : -40°C to 85°C
• Available in Pb-free QFN-32 and LQFP-32 packages (RoHS compliant).

FT313H – Hi-Speed Host Controller <---- I see address, data and chip select pins there!!

• USB 2.0 Hi-Speed Host, EHCI compatible, single port IC
• Supports multiple bus interfaces. 8-bit or 16-bit bus for GPIO, SRAM or NOR Flash
• Support Bulk, Isochronous, Control and Interrupt transfers
• Split transaction support for external USB hubs
• Single power supply operation at 3.3V
• 1.8V, 2.5V and 3.3V IO levels supported
• 24kBytes high speed RAM memory
• Battery Charger Emulation (BCD 1.2) to allow downstream devices to request higher currents
• Extended operating temperature range : -40°C to 85°C.
• Available in Pb-free QFN-64, LQFP-64 and TQFP-64 packages (RoHS compliant).

So? Am I wrong with FTDI's FT313H – Hi-Speed Host Controller?

It's a host controller chip, and it does feature address, data and chip select pins, so... I think it could be interfaced directly with a 65xx MCPU, couldn't it??

Potentially. I see that it implements the EHCI spec, which is common to most general-purpose USB 2.0 host controllers, including the ones ubiquitously found in PCs.

But now you have to deal with the USB protocol in all its labyrinthine complexity. You should seriously research what you're getting into in that respect; I suggest starting with a bare-metal boot tutorial for the Raspberry Pi, and note that the basic code for interfacing with a USB keyboard is provided for you instead of being a type-in. Study that code.