UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
699 of 1441
NXP Semiconductors
UM10503
Chapter 25: LPC43xx/LPC43Sxx USB0 Host/Device/OTG controller
25.9.2.1 Determining the number of packets for Isochronous IN endpoints
The following examples show how the MULT field in the dQH and the MultO in the dTD
are used to control the number of packets sent in an In-transaction for an isochronous
endpoint:
Example 1
MULT = 3; Max_packet_size = 8; Total_bytes = 15; MultO = 0 (default)
RO
11:10
MultO
for an example)
This field can be used for transmit ISOs to override the MULT
field in the dQH. This field must be zero for all packet types
that are not transmit-ISO.
00 - Execute N transactions as demonstrated by the USB
variable length protocol where N is computed using
Max_packet_length and the Total_bytes field in the dTD.
01 - Execute one transaction
10 - Execute two transactions
11 - Execute three transactions
Remark:
Non-ISO and Non-TX endpoints must set
MultO=”00”.
9:8
- reserved
R/W
7:0
Status
Status
This field is used by the device controller to communicate
individual execution states back to the software. This field
contains the status of the last transaction performed on this
dTD.
Bit 7 = 1 - status: Active
Bit 6 = 1 - status: Halted
Bit 5 = 1 - status: Buffer Error
Bit 4 - reserved
Bit 3 = 1 - status: Transaction Error
Bit 2 - reserved
Bit 1 - reserved
Bit 0 - reserved
Table 509. dTD buffer page pointer list
Access
Bit
Name
Description
RO
31:12
BUFF_P
Selects the page offset in memory for the packet buffer.
Non-virtual memory systems will typically set the buffer
pointers to a series of incrementing integers.
page 0:
11:0
CURR_OFFS
Offset into the 4 kB buffer where the packet is to begin.
page 1:
10:0
FRAME_N
Written by the device controller to indicate the frame
number in which a packet finishes. This is typically
used to correlate relative completion times of packets
on an isochronous endpoint.
Table 508. dTD token
…continued
Access
Bit
Name
Description