Isochronous Out Endpoint Operation Example - Philips LPC214 Series User Manual

Philips Semiconductors
Volume 1

14.14.4 Isochronous OUT Endpoint Operation Example

For example assume that an isochronous endpoint is programmed for the transfer of 10
frames. After transferring four frames with packet size 10,15, 8 and 20 bytes; the
descriptors and memory map looks as shown in
starts when the internal frame number was 21.
The_total_number_of_bytes_transferred = 0x0A + 0x0F + 0x08 + 0x14 = 0x35.
The sixteenth bit for all the words in the packet length memory will be set to 1.
W0
W1
W2
W3
W4
0x0
W0
0x000A0010
W1
W2 0x80000035
W3 0x4 - -
W4
0x60000010
Fig 55. Isochronous OUT Endpoint operation example
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DMA_buffer_length Max_packet_size
0x000A 0x0
Present_DMA_Count ATLE settings
0x0 NA
Isocronous_packetsize_memory_address
After 4 packets
0x1 0
Frame Number
31
21
22
23
24
Rev. 01 — 15 August 2005
Figure
Next_DD_Pointer
NULL
Isochronous_endpoint Next_DD_Valid
1 0
DMA_buffer_start_addr
0x80000000
Packet_Valid DD_Status
NA 0x0
0x60000000
Packet_Valid PacketLength
16 15
1 10
1 15
1 8
1 20
Packet size memory
UM10139
Chapter 14: USB Device Controller
55. Assuming that the transfer
DMA_mode
0
DD_Retired
0
Full
Empty
0
Data memory
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
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