Texas Instruments TMS320DM357 - Manual (Page 46)

3.2.1.2 IN Data Phase
USB Controller Host and Peripheral Modes Operation www.ti.com
3. At the end of the attempt to send the data, the controller will generate an Endpoint 0 interrupt. The
software should then read HOST_CSR0 to establish whether the RXSTALL bit (bit 2), the ERROR bit
(bit 4) or the NAK_TIMEOUT bit (bit 7) has been set.
If RXSTALL is set, it indicates that the target did not accept the command (e.g., because it is not
supported by the target device) and so has issued a STALL response.
If ERROR is set, it means that the controller has tried to send the SETUP Packet and the following
data packet three times without getting any response.
If NAK_TIMEOUT is set, it means that the controller has received a NAK response to each attempt to
send the SETUP packet, for longer than the time set in HOST_NAKLIMIT0. The controller can then be
directed either to continue trying this transaction (until it times out again) by clearing the
NAK_TIMEOUT bit or to abort the transaction by flushing the FIFO before clearing the NAK_TIMEOUT
bit.
4. If none of RXSTALL, ERROR or NAK_TIMEOUT is set, the SETUP Phase has been correctly ACKed
and the software should proceed to the following IN Data Phase, OUT Data Phase or IN Status Phase
specified for the particular Standard Device Request.
For the IN Data Phase of a control transaction ( Figure 10 ), the software driving the USB host device
needs to:
1. Set REQPKT bit of HOST_CSR0 (bit 5).
2. Wait while the controller sends the IN token and receives the required data back.
3. When the controller generates the Endpoint 0 interrupt, read HOST_CSR0 to establish whether the
RXSTALL bit (bit 2), the ERROR bit (bit 4), the NAK_TIMEOUT bit (bit 7) or RXPKTRDY bit (bit 0) has
been set.
If RXSTALL is set, it indicates that the target has issued a STALL response.
If ERROR is set, it means that the controller has tried to send the required IN token three times without
getting any response.
If NAK_TIMEOUT bit is set, it means that the controller has received a NAK response to each attempt
to send the IN token, for longer than the time set in HOST_NAKLIMIT0. The controller can then be
directed either to continue trying this transaction (until it times out again) by clearing the
NAK_TIMEOUT bit or to abort the transaction by clearing REQPKT before clearing the NAK_TIMEOUT
bit.
4. If RXPKTRDY has been set, the software should read the data from the Endpoint 0 FIFO, then clear
RXPKTRDY.
5. If further data is expected, the software should repeat Steps 1-4.
When all the data has been successfully received, the CPU should proceed to the OUT Status Phase of
the Control Transaction.
Universal Serial Bus (USB) Controller 46 SPRUGH3 – November 2008
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