Datasheet

Section 14 Universal Serial Bus (USB)
Rev.7.00 Dec. 24, 2008 Page 514 of 698
REJ09B0074-0700
USB function Firmware
Receive IN token
Transmit data to host
Write 1 to EP1 FIFO
empty enable
(EP1EMPTYE in UIER1 = 1)
UIFR1/EP1EMPTY interrupt
USB endpoint data register 1
(write one packet of data
to UEDR1)
Write 1 to EP1 packet enable bit
(EP1PKTE in UTRG0 = 1)
Write 0 to EP1 FIFO empty
interrupt enable bit
(EP1EMPTYE in UIER1 = 0)
Set EP1 FIFO empty status
(EP1EMPTY in UIFR1 = 1)
Valid data
in EP1 FIFO?
NAK
ACK
Yes
Yes
Yes
No
No
No
Clear EP1 FIFO empty status
(EP1EMPTY in UIFR1 = 0)
Space
in EP1 FIFO?
No
Yes
EXIRQx
Is there
data to be transmitted
to host?
Is there
data to be transmitted
in host?
Figure 14.18 EP1 Bulk-In Transfer Operation