OXFORD SEMICONDUCTOR, INC.
OXCFU950 DATA SHEET
2
2.1
F
UNCTIONAL
O
VERVIEW
Introduction
Traditional OHCI host controllers use memory on the host
system, which is not possible for a CompactFlash card, so
the OXCFU950 provides 8 Kbytes of on-board RAM for this
purpose, which can be accessed via the common memory
space and is large enough to contain all the required
structures.
The OXCFU950 provides a multi-function CompactFlash
interface to a USB 1.1 FS host controller and UART
interface. Figure 1 shows the structure of the device. The
OXCFU950 provides two functions: USB and UART; and
three spaces: attribute memory, common memory and I/O
space. It can also be configured, with software support, as
a single-function CompactFlash card, supporting either
USB-only or UART-only operation. Note: the hardware
underpinning both functions is accessible via single-
function mode, which would facilitate a single-function
hybrid driver able to control both the USB and UART
functions, if required.
2.4
I/O Space
The I/O space in the OXCFU950 contains three register
sets that allow access to local configuration registers
(LCRs), USB registers and UART registers. The registers
become available when the functions are enabled (via the
FCRs).
The LCRs provide access to the OXCFU950 non-USB and
non-UART functions. They also provide a mechanism to
start and stop clocks within the device and to generate a
soft reset to the USB controller and UART controller.
The UART register set is compatible with the 950, but has
been extended to allow higher performance with many host
controllers.
The USB register set provides indirect 32-bit access to
both an OHCI-compatible register set and the common
memory space.
2.2
Attribute Memory
The attribute memory space contains the card information
structure (CIS) (see PCMCIA metaformat specification),
and a set of function configuration registers (FCRs) (see
PCMCIA electrical specification) for each function (USB
and UART).
A CompactFlash host initially reads the CIS from the
attribute memory to establish the features and
requirements of the OXCFU950. The OXCFU950 provides
a default hardwired version of the CIS and a user-
programmable version of the CIS in EEPROM; see Section
5 for details. The CIS is read-only, but programming the
internal EEPROM can change its contents. This allows the
OXCFU950 to be used in many different applications and
allows product differentiation.
Each function must be configured and enabled by the host
by accessing the appropriate FCRs, which exist at a
specific location in attribute memory. The CIS tells the host
where the FCRs for each function can be found.
2.5
USB Host Controller
The USB host controller is based on an embedded OHCI
model. It provides a single USB 2.0 full-speed (FS) port. A
device driver is required on the host PC to access the port,
because the OHCI registers must be accessed indirectly,
due to limitations of the CompactFlash/CF+ and PCMCIA
16-bit PC Card standards.
It is possible to create a device driver that will allow a
specific USB device to be accessed via the CompactFlash
interface. This could, for example, be used in a product
without a public USB interface, where a known USB
peripheral is always present.
It is also possible to create a device driver that is integrated
into the USB stack of the host operating system USB stack.
This is ideal for a solution that includes a public USB
interface, or for a solution that interfaces into a USB
peripheral with existing drivers that could be used with the
OS USB stack.
Note: The USB controller supports all OHCI endpoint
types. However, support is not provided for USB hub
devices.
2.3
Common Memory
The USB host controller used in the OXCFU950 is based
on the OHCI standard, which defines how the OS and USB
host controller communicate. OHCI host controllers use an
area of memory and a standard register set. Structures that
describe packets that are to be transmitted or have been
received are built up in memory, and are read or written by
the USB host controller or operating system (OS).
DS-0023 February 2007
External—Free Release
Page 8 of 74
OXFORD [ OXFORD SEMICONDUCTOR ]
