12-18
MCF5272 User’s Manual
Register Description and Programming Model
14
RESUME
Generates RESUME condition. Used to exit the SUSPEND state. The USB control logic
ensures the forced resume duration is greater than 10 ms. This command bit is write-only
and always returns 0 when read.
0 Default
1 Generate RESUME condition (force data lines to K state)
Note: this command generates a RESUME only if the USB is both suspended and
enabled for remote wakeup by the host, that is, USBEPSR0[WAKE_ST] = 1.
13
AFE_EN
External USB analog front-end enable. Used to select the internal or external USB
analog front end (AFE). The internal AFE is selected by default.
0 The USB internal AFE is powered up and the external transceiver interface is disabled.
The driven outputs can be observed on the parallel port A signals if they are configured
for USB.
1 The USB internal AFE is powered down and the external transceiver interface is
enabled. The internal transceiver outputs, (USBH and USBL), are high impedance.
12
BUS_PWR
Select bus-powered mode. Used to select between bus-powered and self-powered
mode. This bit only affects the response to a GET_STATUS device request. This bit
should be set according to the current configuration.
0 Self-powered mode
1 Bus-powered mode
11
USB_EN
Enables and disables the USB control logic. Has no effect on USB register values. When
cleared, the outputs are high impedance, preventing any response to the host. This bit
should be set after USB module registers are initialized and the descriptors are copied
into the configuration RAM.
0 Disable USB module
1 Enable USB module
10
CFG_RAM_VAL
Enable USB configuration RAM. Notifies the USB module that the user has loaded the
configuration RAM. Must be set in order for the USB module to process the USB
standard device requests that access the configuration RAM. These requests are
GET
_
DESCRIPTOR
,
SET
_
CONFIGURATION
, and
SET
_
INTERFACE
. When this bit is set,
accesses to the configuration RAM cause an access error.
0 Configuration RAM invalid
1 Configuration RAM valid
9
CMD_ERR
Command error for device request interface. Used to indicate to the endpoint controller
that an error has been encountered during class or vendor specific device request or
SYNCH_FRAME command processing. This command bit is write only and always
returns 0 when read.
Result of Request
CMD_OVER
CMD_ERR
Processed device request successfully
1
0
Error processing the request
1
1
Busy processing the request
0
X
Note: CMD_OVER and CMD_ERR have to be written simultaneously. The CMD_OVER
and CMD_ERR bits control the status stage response for vendor and class specific
requests.
8
CMD_OVER
Command over for device request interface. Used to indicate to the endpoint controller
that processing of a class or vendor specific device request or SYNCH_FRAME
command has been completed by the user. This command bit is write only and always
returns 0 when read.
Note: CMD_OVER and CMD_ERR have to be written simultaneously. The CMD_OVER
and CMD_ERR bits control the status stage response for vendor and class specific
requests.
Table 12-12. EP0CTL Field Descriptions (Continued)
Bits
Name
Description
Содержание DigitalDNA ColdFire MCF5272
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