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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
698 of 1441
NXP Semiconductors
UM10503
Chapter 25: LPC43xx/LPC43Sxx USB0 Host/Device/OTG controller
Table 508. dTD token
Access
Bit
Name
Description
-
31
-
reserved
R/W
30:16
Total_bytes
Total bytes
This field specifies the total number of bytes to be moved with
this transfer descriptor. This field is decremented by the
number of bytes actually moved during the transaction and it
is decremented only when the transaction has been
completed successfully.
The maximum value software can write into this field is
0x5000 (5 x 4 kB) for the maximum number of bytes five page
pointers can access. Although it is possible to create a
transfer up to 20 kB this assumes that the first offset into the
first page is zero. When the offset cannot be predetermined,
crossing past the fifth page can be guaranteed by limiting the
total bytes to 16 kB. Therefore, the maximum recommended
Total-Bytes = 16 kB (0x4000).
If Total_bytes = 0 when the host controller fetches this
transfer descriptor and the active bit is set in the Status field
of this dTD, the device controller executes a zero-length
transaction and retires the dTD.
Remark:
For IN transfers, it is not a requirement that
Total_bytes is an even multiple of Max_packet_length. If
software builds such a dTD, the last transaction will always be
less than Max_packet_length.
RO
15
IOC
Interrupt on complete
This bit is used to indicate if USBINT will be set when the
device controller is finished with this dTD.
1 - USBINT set.
0 - USBINT not set.
-
14:12
-
reserved