Document No.: FT_000138
VINCULUM-II EMBEDDED DUAL USB HOST CONTROLLER IC Datasheet
Version -
1.2
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.
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.
Isochronous Transfer: Used for transferring data that requires a constant delivery rate e.g.
web cam, wireless modem.
Control Transfer: Used to transfer specific requests to all types USB devices (most commonly
used during device configuration).
USB 2.0 - 480Mb/s (High Speed) transactions shall not be supported as the power requirements are
deemed excessive for VNC2 target applications. VNC2 configured to Full speed is 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 like a USB device. 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 not both at the same
time. The following diagrams in figure 7.1 give examples of possible modes of operation:
Port
0
USB Device
Port
0
USB Host
VNC2
VNC2
Port
1
BOMS Flash Disk
Port
1
Port 0 and 1 in Host mode
Port 0 in Slave mode
Port
0
Port
0
USB Host
VNC2
VNC2
USB Host
Port
1
BOMS Flash Disk
Port
1
USB Host
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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