Datasheet

Table Of Contents
Section 15 Universal Serial Bus Interface (USB)
REJ09B0140-0900 Rev. 9.00 Page 563 of 846
Sep 16, 2010
H8S/2215 Group
15.5.5 Interrupt-In Transfer (EP1i Is specified as Endpoint)
USB function Firmware
Receive IN token
Transmit data to host
Set EP1i transmit
complete flag
(EP1iTS in UIFR0 = 1)
Write data to USB endpoint
data register 1i (UEDR1i)
Write 1 to EP1i packet
enable bit
(EP1iPKTE in UTRG0 = 1)
Clear EP1i transmit
complete flag
(EP1iTS in UIFR0 = 0)
Write data to USB endpoint
data register 1i (UEDR1i)
Write 1 to EP1i packet
enable bit
(EP1iPKTE in UTRG0 = 1)
Valid data
in EP1iFIFO?
Is there
transmit data
to host?
Is there
transmit data
to host?
No
Yes
No
Yes
No
Yes
NAK
ACK
Note: This flowchart shows just one example of interrupt transfer processing. Other possibilities include an
operation flow in which, if there is data to be transferred, the EP1i data enable bit in the USB data status
register is referenced to confirm that the FIFO is empty, and then data is written to the FIFO.
Interrupt request
Figure 15.18 EP1i Interrupt-In Transfer Operation