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->NEC uPD985xx USB Device Driver</TITLE
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-><H1
-><A
-NAME="DEVS-USB-NEC-UPD985XX">NEC uPD985xx USB Device Driver</H1
-><DIV
-CLASS="REFNAMEDIV"
-><A
-NAME="AEN18819"
-></A
-><H2
->Name</H2
->NEC uPD985xx USB Support -- Device driver for the on-chip NEC uPD985xx USB device</DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN18822"
-></A
-><H2
->NEC uPD985xx USB Hardware</H2
-><P
->The NEC uPD985xx family of processors is supplied with an on-chip USB
-slave device, the UDC (USB Device Controller). This supports seven
-endpoints. Endpoint 0 can only be used for control messages. Endpoints
-1 and 2 are for isochronous transmits and receives respectively.
-Endpoints 3 and 4 support bulk transmits and receives. Endpoints 5 and
-6 normally support interrupt transmits and receives, but endpoint 5 can
-also be configured to support bulk transmits. At this time only the
-control endpoint 0, the bulk endpoints 3 and 4, and the interrupt
-endpoint 5 are supported.</P
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN18825"
-></A
-><H2
->Endpoint Data Structures</H2
-><P
->The uPD985xx USB device driver can provide up to four data structures
-corresponding to the four supported endpoints: a
-<SPAN
-CLASS="STRUCTNAME"
->usbs_control_endpoint</SPAN
-> structure
-<TT
-CLASS="VARNAME"
->usbs_upd985xx_ep0</TT
->;
-<SPAN
-CLASS="STRUCTNAME"
->usbs_tx_endpoint</SPAN
-> structures
-<TT
-CLASS="VARNAME"
->usbs_upd985xx_ep3</TT
-> and
-<TT
-CLASS="VARNAME"
->usbs_upd985xx_ep5</TT
->; and a
-<SPAN
-CLASS="STRUCTNAME"
->usbs_rx_endpoint</SPAN
->
-<TT
-CLASS="VARNAME"
->usbs_upd985xx_ep4</TT
->. The header file
-<TT
-CLASS="FILENAME"
->cyg/io/usb/usbs_nec_upd985xx.h</TT
->
-provides declarations for these.</P
-><P
->Not all applications will require support for all the endpoints. For
-example, if the intended use of the UDC only involves peripheral to
-host transfers then <TT
-CLASS="LITERAL"
->usbs_upd985xx_ep4</TT
-> is redundant.
-The device driver provides configuration options to control the
-presence of each endpoint:</P
-><P
-></P
-><OL
-TYPE="1"
-><LI
-><P
->Endpoint 0 is controlled by
-<TT
-CLASS="LITERAL"
->CYGFUN_DEVS_USB_UPD985XX_EP0</TT
->. This defaults to
-enabled if there are any higher-level packages that require USB
-hardware or if the global preference
-<TT
-CLASS="LITERAL"
->CYGGLO_IO_USB_SLAVE_APPLICATION</TT
-> is enabled,
-otherwise it is disabled. Usually this has the desired effect. It may
-be necessary to override this in special circumstances, for example if
-the target board uses an external USB chip in preference to the UDC
-and it is that external chip's device driver that should be used
-rather than the on-chip UDC. It is not possible to disable endpoint 0
-and at the same time enable one or both of the other endpoints, since
-a USB device is only usable if it can process the standard control
-messages.</P
-></LI
-><LI
-><P
->Endpoint 3 is controlled by
-<TT
-CLASS="LITERAL"
->CYGPKG_DEVS_USB_UPD985XX_EP3</TT
->. By default this
-endpoint is disabled: according to NEC erratum U3 there may be
-problems when attempting bulk transfers of 192 bytes or greater. As an
-alternative the device driver provides support for endpoint 5,
-configured to allow bulk transfers. Endpoint 3 can be enabled if the
-application only requires bulk transfers of less than 192 bytes, or if
-this erratum is not applicable to the system being developed for other
-reasons.</P
-></LI
-><LI
-><P
->Endpoint 4 is controlled by
-<TT
-CLASS="LITERAL"
->CYGPKG_DEVS_USB_UPD985XX_EP4</TT
->. This is enabled by
-default whenever endpoint 0 is enabled, but it can be disabled
-manually.</P
-></LI
-><LI
-><P
->Endpoint 5 is controlled by
-<TT
-CLASS="LITERAL"
->CYGPKG_DEVS_USB_UPD985XX_EP5</TT
->. This is enabled by
-default whenever endpoint 0 is enabled, but it can be disabled
-manually. There is also a configuration option
-<TT
-CLASS="LITERAL"
->CYGIMP_DEVS_USB_UPD985XX_EP5_BULK</TT
->, enabled by
-default. This option allows the endpoint to be used for bulk
-transfers rather than interrupt transfers.</P
-></LI
-></OL
-><P
->The uPD985xx USB device driver implements the interface specified by the
-common eCos USB Slave Support package. The documentation for that
-package should be consulted for further details. </P
-><P
->The device driver assumes a bulk packet size of 64 bytes, so this
-value should be used in the endpoint descriptors in the enumeration
-data provided by application code. The device driver also assumes
-a control packet size of eight bytes, and again this should be
-reflected in the enumeration data. If endpoint 5 is configured for
-interrupt rather than bulk transfers then the maximum packet size is
-limited to 64 bytes by the USB standard.</P
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN18855"
-></A
-><H2
->Devtab Entries</H2
-><P
->In addition to the endpoint data structures the uPD985xx USB device
-driver can also provide devtab entries for each endpoint. This allows
-higher-level code to use traditional I/O operations such as
-<TT
-CLASS="FUNCTION"
->open</TT
->/<TT
-CLASS="FUNCTION"
->read</TT
->/<TT
-CLASS="FUNCTION"
->write</TT
->
-rather than the USB-specific non-blocking functions like
-<TT
-CLASS="FUNCTION"
->usbs_start_rx_buffer</TT
->. These devtab entries are
-optional since they are not always required. The relevant
-configuration options are
-<TT
-CLASS="LITERAL"
->CYGVAR_DEVS_USB_UPD985XX_EP0_DEVTAB_ENTRY</TT
->,
-<TT
-CLASS="LITERAL"
->CYGVAR_DEVS_USB_UPD985XX_EP3_DEVTAB_ENTRY</TT
->,
-<TT
-CLASS="LITERAL"
->CYGVAR_DEVS_USB_UPD985XX_EP4_DEVTAB_ENTRY</TT
->, and
-<TT
-CLASS="LITERAL"
->CYGVAR_DEVS_USB_UPD985XX_EP5_DEVTAB_ENTRY</TT
->. By
-default these devtab entries are provided if the global preference
-<TT
-CLASS="LITERAL"
->CYGGLO_USB_SLAVE_PROVIDE_DEVTAB_ENTRIES</TT
-> is enabled,
-which is usually the case. Obviously a devtab entry for a given
-endpoint will only be provided if the underlying endpoint is enabled.
-For example, there will not be a devtab entry for endpoint 4 if
-<TT
-CLASS="LITERAL"
->CYGPKG_DEVS_USB_UPD985XX_EP4</TT
-> is disabled.</P
-><P
->The names for the devtab entries are determined by using a
-configurable base name and appending <TT
-CLASS="LITERAL"
->0c</TT
->,
-<TT
-CLASS="LITERAL"
->3w</TT
->, <TT
-CLASS="LITERAL"
->4r</TT
-> or <TT
-CLASS="LITERAL"
->5w</TT
->.
-The base name is determined by the configuration option
-<TT
-CLASS="LITERAL"
->CYGDAT_DEVS_USB_UPD985XX_DEVTAB_BASENAME</TT
-> and has a
-default value of <TT
-CLASS="LITERAL"
->/dev/usbs</TT
->, so the devtab entry for
-endpoint 4 would default to <TT
-CLASS="LITERAL"
->/dev/usbs4r</TT
->. If the
-target hardware involves multiple USB devices then application
-developers may have to change the base name to prevent a name clash
-with other USB device drivers.</P
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN18876"
-></A
-><H2
->Restrictions</H2
-><P
->The current device driver imposes a restriction on certain bulk
-receives on endpoint 4. If the protocol being used involves
-variable-length transfers, in other words if the host is allowed to
-send less data than a maximum-sized transfer, then the buffer passed
-to the device driver for receives must be aligned to a 16-byte
-cacheline boundary and it must be a multiple of this 16-byte cacheline
-size. This restriction does not apply if the protocol only involves
-fixed-size transfers.</P
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN18879"
-></A
-><H2
->Optional Hardware Workarounds</H2
-><P
->The NEC errata list a number of other problems that affect the USB
-device driver. The device driver contains workarounds for these, which
-are enabled by default but can be disabled if the application
-developer knows that the errata are not relevant to the system being
-developed.</P
-><P
->Erratum S1 lists a possible problem if the device driver attempts
-multiple writes to the USB hardware. This is circumvented by a
-dummy read operation after every write. If the workaround is not
-required then the configuration option
-<TT
-CLASS="LITERAL"
->CYGIMP_DEVS_USB_UPD985XX_IBUS_WRITE_LIMIT</TT
-> can be disabled.</P
-><P
->Errata U3 and U4 describe various problems related to concurrent
-transmissions on different endpoints. By default the device driver
-works around this by serializing all transmit operations. For example
-if the device driver needs to send a response to a control message on
-endpoint 0 while there is an ongoing bulk transfer on endpoint 5, the
-response is delayed until the bulk transfer has completed. Under
-typical operating conditions this does not cause any problems:
-endpoint 0 traffic usually happens only during initialization, when
-the target is connected to the host, while endpoint 5 traffic only
-happens after initialization. However if transmit serialization is
-inappropriate for the system being developed then it can be disabled
-using the configuration option
-<TT
-CLASS="LITERAL"
->CYGIMP_DEVS_USB_UPD985XX_SERIALIZE_TRANSMITS</TT
->. </P
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN18886"
-></A
-><H2
->Platform Dependencies</H2
-><P
->On some platforms it is necessary for the low-level USB device driver
-to perform some additional operations during start-up. For example it
-may be necessary to manipulate one of the processor's GPIO lines
-before the host can detect a new USB peripheral and attempt to
-communicate with it. This avoids problems if the target involves a
-significant amount of work prior to device driver initialization, for
-example a power-on self-test sequence. If the USB host attempted to
-contact the target before the USB device driver had been initialized,
-it would fail to get the expected responses and conclude that the
-target was not a functional USB peripheral.</P
-><P
->Platform-specific initialization code can be provided via a macro
-<TT
-CLASS="FUNCTION"
->UPD985XX_USB_PLATFORM_INIT</TT
->. Typically this macro
-would be defined in the platform HAL's header file
-<TT
-CLASS="FILENAME"
->cyg/hal/plf_io.h</TT
->. If the
-current platform defines such a macro, the USB device driver will
-invoke it during the endpoint 0 start-up operation.</P
-></DIV
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