OM11077 NXP Semiconductors, OM11077 Datasheet - Page 382

• Manufacturer Part Number: OM11077
• Description: MODULE DIMM LPC2478 ARM7
• Manufacturer: NXP Semiconductors

Specifications of OM11077

• Accessory Type: Module Card
• For Use With/related Products: ARM-57TS-LPC2478
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 568-4742

NXP Semiconductors
UM10237_4
User manual
14.6.4 DMA descriptor completion
14.6.5 Isochronous OUT Endpoint Operation Example
The isochronous packet size is stored in memory as shown in
the packet size memory shown is divided into fields: Frame_number (bits 31 to 17),
Packet_valid (bit 16), and Packet_length (bits 15 to 0). The space allocated for the packet
size memory for a given DD should be DMA_buffer_length words in size – one word for
each packet to transfer.
OUT endpoints
At the completion of each frame, the packet size is written to the address location in
Isochronous_packet_size_memory_address, and
Isochronous_packet_size_memory_address is incremented by 4.
IN endpoints
Only the Packet_length field of the isochronous packet size word is used. For each frame,
an isochronous data packet of size specified by this field is transferred from the USB
device to the host, and Isochronous_packet_size_memory_address is incremented by 4
at the end of the packet transfer. If Packet_length is zero, an empty packet will be sent by
the USB device.
DDs for isochronous endpoints can only end with a status code of NormalCompletion
since there is no short packet on Isochronous endpoints, and the USB transfer continues
indefinitely until a SystemError occurs. There is no DataOverrun detection for isochronous
endpoints.
Assume that an isochronous endpoint is programmed for the transfer of 10 frames and
that the transfer begins when the frame number is 21. After transferring four frames with
packet sizes of 10,15, 8 and 20 bytes without errors, the descriptor and memory map
appear as shown in
The_total_number_of_bytes_transferred = 0x0A + 0x0F + 0x08 + 0x14 = 0x35.
The Packet_valid bit (bit 16) of all the words in the packet length memory is set to 1.
Figure
Rev. 04 — 26 August 2009
13–49.
Chapter 13: LPC24XX USB device controller
Figure
13–49. Each word in
UM10237
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