Chapter 12. Universal Serial Bus (USB)
12-19
Register Description and Programming Model
12.3.2.14 USB Endpoint 1–7 Control Register (EPnCFG)
Figure 12-17 shows the USB endpoint 1–7 control register.
7
CRC_ERR
CRC error generation enable. This bit enables CRC error generation for debug and test
purpose. In order to use this feature, the DEBUG bit must be set. Enabling this bit causes
a CRC error on the next data packet transmitted. The CRC_ERR bit must be set again in
order to generate another CRC error. This bit only applies to IN transfers. This command
bit is write-only and always returns 0 when read.
1 CRC error generation if DEBUG = 1
0 default value
6
—
Reserved, should be cleared.
5–4
OUT_LVL
Endpoint 0 OUT FIFO level for interrupt. This field selects the FIFO level to generate an
OUT_LVL interrupt. The OUT_LVL interrupt is generated when the FIFO fills above the
selected level.
00 FIFO 25% Full
01 FIFO 50% Full
10 FIFO 75% Full
11 FIFO 100% Full
3–2
IN_LVL
Endpoint 0 IN FIFO level for interrupt. This field selects the FIFO level to generate an
IN_LVL interrupt. The IN_LVL interrupt is generated when the FIFO falls below the
selected level.
00 FIFO 25% Empty
01 FIFO 50% Empty
10 FIFO 75% Empty
11 FIFO 100% Empty
1
IN_DONE
This bit controls the USB's response to IN tokens from the host. This bit is set at Reset
and must be cleared by software when the last byte of a transfer has been written to the
IN-FIFO. This bit is then subsequently set by the USB core when an end of transfer (EOT)
event occurs indicating that the transfer has been completed. An end of transfer (EOT)
event is indicated by one of the following:
a) An IN packet is transmitted that contains less than the maximum number of bytes
defined at endpoint configuration.
b) A zero length IN packet is transmitted. This occurs when the previously transmitted
IN packet was full, and no more data remains in the IN-FIFO. Hence a single zero
length packet must be sent to indicate EOT.
0 CPU has completed writing to the IN-FIFO and transfer is in progress. The USB
module will send any amount of data in the FIFO or a zero-length packet when the
FIFO is empty.
1 Transfer completed or CPU Busy writing transfer into the IN-FIFO. The USB module
will only send maximum size packets or NAK responses if the FIFO contains less than
a maximum size packet. This bit is set at Reset and on an EOT event.
0
—
Reserved, should be cleared.
Table 12-12. EP0CTL Field Descriptions (Continued)
Bits
Name
Description
Содержание DigitalDNA ColdFire MCF5272
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