UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 382 o f 792
NXP Semiconductors UM10237
Chapter 13: LPC24XX USB device controller
14.7 Auto Length Transfer Extraction (ATLE) mode operation

Some host drivers such as NDIS (Network Driver Interface Specification) host drivers are

capable of concatenating small USB transfers (delta transfers) to form a single large USB

transfer. For OUT USB transfers, the device hardware has to break up this concatenated

transfer back into the original delta transfers and transfer them to separate DMA buffers.

This is achieved by setting the DMA mode to Auto Transfer Length Extraction (ATLE)

mode in the DMA descriptor. ATLE mode is supported for Bulk endpoints only.

OUT transfers in ATLE mode

Fig 49. Isochronous OUT endpoint operation example

DMA_modeNext_DD_ValidIsochronous_endpointMax_packet_sizeDMA_buffer_length
01631
after 4 packets
15
0x60000010
0x80000035
0x000A0010
0x4
0x0
W1
W2
W3
W4
W0
FULL
EMPTY
data memory
packet size memory
0x60000000
0x80000000
W1
W2
W3
W4
W0
0010x00x000A
Next_DD_Pointer
NULL
DMA_buffer_start_addr
Isocronous_packetsize_memory_address
DD_RetiredDD_StatusPacket_ValidATLE settingsPresent_DMA_Count
0x0 0NANA
0x0
Packet_Lengthframe_ number Packet_Valid
10
15
8
20
1
1
1
1
21
22
23
24
00x1--