H8SXSLASH1663R datasheet(1058/1504 Pages) RENESAS

1058 / 1504 page

Section 20 USB Function Module (USB)

Rev. 2.00 Sep. 24, 2008 Page 1026 of 1468

REJ09B0412-0200

20.8

DMA Transfer

20.8.1

Overview

DMA transfer can be performed for endpoints 1 and 2 in this module. Note that word or longword

data cannot be transferred.

When endpoint 1 holds at least one byte of valid receive data, a DMA request for endpoint 1 is

generated. When endpoint 2 holds no valid data, a DMA request for endpoint 2 is generated.

If the DMA transfer is enabled by setting the EP1DMAE bit in the DMA transfer setting register

to 1, zero-length data reception at endpoint 1 is ignored. When the DMA transfer is enabled, the

RDFN bit for EP1 and PKTE bit for EP2 do not need to be set to 1 in TRG (note that the PKTE bit

must be set to 1 when the transfer data is less than the maximum number of bytes). When all the

data received at EP1 is read, the FIFO automatically enters the EMPTY state. When the maximum

number of bytes (64 bytes) are written to the EP2 FIFO, the FIFO automatically enters the FULL

state, and the data in the FIFO can be transmitted (see figures 20.22 and 20.23).

20.8.2

DMA Transfer for Endpoint 1

When the data received at EP1 is transferred by the DMA, the USB function module automatically

performs the same processing as writing 1 to the RDFN bit in TRG if the currently selected FIFO

becomes empty. Accordingly, in DMA transfer, do not write 1 to the RDFN bit for EPI in TRG. If

the user writes 1 to the RDFN bit in DMA transfer, correct operation cannot be guaranteed.

Figure 20.22 shows an example of receiving 150 bytes of data from the host. In this case, internal

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

three times. This internal processing is performed when the currently selected data FIFO becomes

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

and when data less than 64 bytes is sent.

RDFN

(Automatically

performed)

RDFN

(Automatically

performed)

RDFN

(Automatically

performed)

64 bytes

22 bytes

Figure 20.22 RDFN Bit Operation for EP1

H8SX/1663R Datasheet(PDF) 1058 Page - Renesas Technology Corp