Datasheet

Table Of Contents
Section 15 Universal Serial Bus Interface (USB)
REJ09B0140-0900 Rev. 9.00 Page 547 of 846
Sep 16, 2010
H8S/2215 Group
15.5 Communication Operation
15.5.1 Initialization
The USB must be initialized as described in the flowchart in figure 15.3.
Cancel power-on reset
USB function Firmware
No
Ye s
Set each interrupt
Start USB operationg clock
oscillation
USB operating clock
stabilization time has
passed?
Cancel USB module stop
mode
Clear MSTPB0 in MSTPCRB
to 0
Clear CK48READY in UIFR3
to 0
Stop USB module operation
Write MSTPB0 in MSTPCRB to 1
Wait for USB cable
connection
Ye s
Ye s
No
No
(Bus powered)
(Self powered)
To USB cable
connecting procedure
Enter software standby state
(If necessary)
Set each interrupt
Wait for USB operating
clock stabilization
USB interface operation OK
Set EPINFO
USB operating clock
stabilization detection
interrupt occurs
Cancel USB interface reset
Clear UIFRST in UCTLR
to 0
Set EPINFO
Write 115-byte data to
UEPIR00_0 to UEPIR22_4
Self powered?
System
enters power-down
mode?
Select USB operating clock
Write UCKS3 to UCKS0
in UCTLR
15.5.2 to (1)
*
*
*
EXIRQ0
Note: Before entering the software standby state, USB module operation must be stopped by setting the
MSTPB0 bit in MSTPCRB register to 1.
Figure 15.3 USB Initialization