Datasheet
Vinculum-II Embedded Dual USB Host Controller IC
Version 1.7
Document No.: FT_000138 Clearance No.: FTDI#143
7 USB Interfaces
VNC2 has two USB 1.1 and USB 2.0 compliant interfaces available either as a USB host or slave device
capable of supporting 1.5Mb/s (Low Speed) and 12Mb/s (full Speed) transactions. The USB specification
defines 4 transfer types that are all supported by VNC2:
Interrupt transfer: Used for legacy devices where the device is periodically polled to see if the
device has data to transfer e.g. Mouse, Keyboard. VNC2 interrupt transfers are valid for low- and
full-speed transactions.
Bulk transfer: Used for transferring large blocks of data that have no periodic or transfer rate
requirement e.g. USB to RS232 (FT232R device), memory sticks. VNC2 bulk transfers are only
valid for full-speed transactions.
Isochronous transfer: Used for transferring data that requires a constant delivery rate e.g. web
cam, wireless modem. VNC2 isochronous transfers are only valid for full-speed transactions.
Control transfer: Used to transfer specific requests to all types USB devices (most commonly
used during device configuration). VNC2 control transfers are valid for low- and full-speed
transfers.
USB 2.0 - 480Mb/s (High Speed) transactions are not supported as the power requirements are deemed
excessive for VNC2 target applications. VNC2 configured to Full speedis supported.
VNC2 has two main USB modes of operation: host mode or client (or Slave) mode. As a client, VNC2 is
able to connect to a PC and act as a USB peripheral. At the same time as being a client the second USB
interface is also able to act as a host and connect to a second USB device using two separate ports (i.e.
Port 0 – Host Port 1- Client). Each USB interface can be either a host or a client. It is not possible to
change from host to client or client to host “on-the-fly”. The following diagrams in figure 7.1 give
examples of possible modes of operation:
USB Device
Port 0
Port 0
USB Host
VNC2
VNC2
Port 1
Port 1
BOMS Flash Disk
Port 0 in Slave mode
Port 0 and 1 in Host mode
Port 0
Port 0
USB Host
USB Host
USB Host
VNC2
VNC2
Port 1
Port 1
BOMS Flash Disk
Port 0 in Slave mode and Port 1 in Host mode
Port 0 and 1 in Slave mode (Null Modem type application)
Figure 7.1 USB Modes
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