H8SXSLASH1663 datasheet(862/1158 Pages) RENESAS

862 / 1158 page

Section 16 USB Function Module (USB)

Rev.1.00 Jun. 07, 2006 Page 810 of 1102

REJ09B0294-0100

16.8.3

DMA Transfer for Endpoint 2

When the transmit data at EP2 is transferred by the DMAC, the USB function module

automatically performs the same processing as writing 1 to the PKTE bit in TRG if the currently

selected FIFO (64 bytes) becomes full. Accordingly, to transfer data of a multiple of 64 bytes, the

user need not write 1 to the PKTE bit. To transfer data of less than 64 bytes, the user must write 1

to the PKTE bit using the DMA transfer end interrupt of the on-chip DMAC. If the user writes 1

to the PKTE bit when the maximum number of bytes (64 bytes) are transferred, correct operation

cannot be guaranteed.

Figure 16.21 shows an example for transmitting 150 bytes of data to the host. In this case, internal

processing which is the same as writing 1 to the PKTE bit in TRG is automatically performed

twice. This internal processing is performed when the currently selected data FIFO becomes full.

Accordingly, this processing is automatically performed only when 64-byte data is sent.

When the last 22 bytes are sent, the internal processing for writing 1 to the PKTE bit is not

performed, and the user must write 1 to the PKTE bit by software. In this case, the application has

no more data to transfer but the USB function module continues to output DMA requests for EP2

as long as the FIFO has an empty space. When all data has been transferred, write 0 to the

EP2DMAE bit in DMAR to cancel DMA requests for EP2.

PKTE

(Automatically

performed)

PKTE

(Automatically

performed)

PKTE is

not performed

Execute by DMA transfer

end interrupt (user)

64 bytes

22 bytes

Figure 16.21 PKTE Bit Operation for EP2

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