OXCFU950_07 Datasheet, PDF (15/74 Pages) Oxford Semiconductor – USB/UART multi-function 16-bit PC Card device

OXFORD SEMICONDUCTOR, INC.
5 CONFIGURATION & OPERATION
5.1 Mode Selection
The OXCFU950 has two modes of operation, as shown in
the table below.
CIS_MODE pin
1
0
Operation
Normal mode
Generic mode
Table 4: Modes of Operation
5.1.1 Normal Mode
The chip usually operates in normal mode, in which the
contents of the EEPROM are used to define the CIS and
the action taken on a USB/UART reset. If no CIS is found
in the EEPROM, the hard-wired CIS is used.
5.1.2 Generic Mode
Generic mode disables the EEPROM controller. It forces
the OXCFU950 to use the hardwired CIS. Under normal
circumstances it should not be used unless an image
placed on the EEPROM provides an invalid CIS. In this
event, it is unlikely that the OXCFU950 can be enumerated
in normal mode, so the contents of the EEPROM can only
be changed by using generic mode.
5.2 16-Bit PC Card & CompactFlash/CF+
Operation
PCMCIA 16-bit PC Card and CompactFlash/CF+ host
systems allow for hot card insertion.
When a card is inserted into a host system, the host
system configures it. The PCMCIA standard defines two
card detect pins that allow the host to be notified when a
card is inserted or removed.
By default the device powers up in either normal or generic
mode, depending on the CIS_MODE pin.
The host system waits for the READY# signal to be active
before reading the CIS in the attribute memory of the
device. By reading this tuple information, the host system is
able to identify the device type and the necessary
resources requested by the device.
OXCFU950 DATA SHEET
The host system then loads the device-driver software
according to the tuple information and configures the I/O,
memory and interrupt resources. After determining that the
device is a memory and I/O type device, the host enables
its I/O mode by writing to its configuration options
register(s) in attribute memory space. Device drivers can
then access the functions at the assigned addresses.
A set of LCRs is provided to control the device
characteristics, such as interrupt handling, and report its
internal functional status.
Two zones in the EEPROM can be used to redefine the
reset values of all the registers in I/O space. One zone is
executed when the USB function is reset; the other is
executed when the UART is reset. In this way the USB and
UART functions can be tailored to end-user requirements if
the default values do not meet the specific requirements of
the manufacturer.
It is good practice to make sure that the EEPROM is
always used to provide reset values for the LCR registers.
Because each function can access any of the LCR
registers, using the EEPROM in this way gives ownership
of each LCR to a specific function. This feature can also be
used to pre-configure the USB or UART registers without
modifying the device driver. This allows, for example, the
enhanced features of the integrated UART to be in place
prior to handing over to any generic device drivers. It is
also possible to pre-configure and then lock four of the
UART registers (CPR, TCR, DLL, DLM), so they cannot be
modified by the device driver.
Device reprogramming can also be performed for the CIS
area, for example to allow the manufacturer to modify the
resources required or manufacturer ID values.
Note: a default set of tuples is provided for both
multifunction and single-function solutions.
DS-0023 February 2007
External—Free Release
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