Datasheet

Section 16 USB Function Module (USB)
R01UH0309EJ0500 Rev. 5.00 Page 1013 of 1408
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
16.8.3 DMA Transfer for Endpoints 1 and 4
When the data received at EP1 is transferred by the DMAC, the USB function module
automatically performs the same processing as writing 1 to the RDFN bit in TRG1 if the currently
selected FIFO becomes empty. Accordingly, in DMA transfer, do not write 1 to the RDFN bit in
TRG1. If the user writes 1 to the RDFN bit in DMA transfer, correct operation cannot be
guaranteed.
Figure 16.21 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 TRG1 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 64 bytes
22 bytes
Figure 16.21 RDFN Bit Operation for EP1