Rev. 3.0, 10/02, page 484 of 686
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
Yes
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
Yes
Yes
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 of 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 UCKS0 to UCKS3
in UCTLR)
15.5.2 to (1)
*
*
*
Note:
Before entering the software standby state, USB module operation must be stopped by setting the
MSTPB0 bit of MSTPCRB register to 1.
Figure 15.3 USB Initialization
Summary of Contents for H8S/2215 Series
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