UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
245 of 362
NXP Semiconductors
UM10208
Chapter 17: LPC2800 USB Device
9.8 Sending data to an IN (TX) endpoint in DMA mode
Software/firmware should program the DMA channel as follows:
1. If necessary, find a free DMA channel (see the last paragraph of
2. Write the channel’s Source (
Address Registers.
3. Write the channel’s Throttle Register (
) for an IN (TX) transfer.
4. Write the channel’s Count Register (
) with the number of bytes to
send.
5. If desired, write the DMA Interrupt Enable Register (
) to enable
interrupt from the channel.
6. Write the channel’s Control Register (
) appropriately for an IN (TX)
transfer from the selected endpoint number, with a non-zero CHEN field, and
optionally to request an interrupt on packet completion or error.
If enabled, an interrupt will occur when the DMA channel has transferred the packet to the
endpoint. Alternatively or in addition, an interrupt from the USB controller can be arranged
after the packet has been sent to the host.