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15.5.5
Interrupt-In Transfer: (EP1i is specified as Endpoint)
USB function
Firmware
IN token reception
Data transmission to host
Set EP1i transmission
complete flag
(UIFR0/EP1i TS = 1)
Write data to USB endpoint
data register 1i (UEDR1i)
Write 1 to EP1i packet
enable bit
(UTRG0/EP1i PKTE = 1)
Clear EP1i transmission
complete flag
(UIFR0/EP1i TS = 0)
Write data to USB endpoint
data register (UEDR1i)
Write 1 to EP1i packet
enable bit
(UTRG0/EP1i PKTE = 1)
Valid data
in EP1i FIFO?
Is there data
for transmission
to host?
Is there data
for transmission
to host?
No
Yes
No
Yes
No
Yes
NACK
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 15.17 EP1i Interrupt-In Transfer Operation
Summary of Contents for H8S/2215 Series
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