Register Map
13-43
USB Function Module
13.2.18
Transmit DMA Control Registers (TXDMA0...TXDMA2)
The read/write transmit DMA control registers (TXDMA...TXDMA2) control the
operation of the transmit DMA channel n (n = 0, 1, 2).
Table 13–19. Transmit DMA Control Registers (TXDMA...TXDMA2)
Bit
Name
Description
15
TXn_EOT
Transmit DMA channel n end of transfer
14
TXn_Start
Transmit DMA channel n start
13–10
–
Reserved
9:0
TXn_TSC
Transmit DMA channel n transfer size counter
13.2.18.1
Transmit DMA Ch.n End of Transfer (TXn_EOT)
This bit can be either 0 or 1 for BULK DMA transfer.
When set to 1 by the local host, it signals to the core that the transfer size set
in TXn_TSC is in bytes. A TX done interrupt (the TXn_Done) is asserted with
the last IN transaction. If the number of bytes set in TXn_TSC is a multiple of
the endpoint buffer size, the TX done interrupt is asserted only after an IN
transaction with an empty data packet.
When cleared, the transfer size set in TXn_TSC is in full buffer size for the end-
point selected (BULK only). A TX done interrupt is asserted when the last buff-
er is sent with the last IN transaction. This mode is to be used for a partial bulk
transfer of a large file exceeding 1023 bytes.
0: DMA transfer size is in buffers.
1: DMA transfer size is in bytes.
Value after local host or USB reset is low.
13.2.18.2
Transmit DMA Ch.n Start (TXn_Start)
Set by the local host to tell the device that the main DMA system is ready to
transmit the number of bytes or buffers. Once set, the DMA transfer cannot be
interrupted, except if the local host clears endpoint in TXDMA_CFG register
(see part 8.8). Writing 0 to this bit has no effect and a read of this bit always
returns 0. The TXn_Done interrupt bit is asserted when the DMA transfer ends.
0: No action
1: DMA transfer start
Always reads 0.