Datasheet

Section 14 Universal Serial Bus (USB)
Rev.7.00 Dec. 24, 2008 Page 529 of 698
REJ09B0074-0700
pointer that controls the internal module FIFO is updated and correct operation cannot be
guaranteed.
14.8.8 Reset
⎯ The manual reset during USB communication operations must not be executed, since the
LSI may stop with the state of USD+ and USD- pins maintained.
This USB module uses synchronous reset for some registers. The reset state of these registers
must be cancelled after the clock oscillation stabilization time has passed. At initialization,
reset must be cancelled using the following procedure:
1. Cancel the USB module stop 1: Clear the USBSTOP1 bit in EXMDLSTP to 0.
2. Select the USB operating clock: Write 1 to the UCKS3 to UCKS0 bits in UCTLR.
3. Cancel the USB module stop 2: Clear the MSTPB0 bit in MSTPCRB to 0.
4. Wait for the USB operating clock stabilization: Wait until the CK48READY bit in UIFR3
is set to 1.
5. Cancel the USB interface reset state: Clear the UIFRST bit in UCTLR to 0.
6. Cancel the UDC core reset state: Clear the UDCRST bit in UCTLR to 0.
For details, see the flowcharts in section 14.5.1, Initialization and section 14.5.2, USB Cable
Connection/Disconnection.
⎯ The USB registers are not initialized when the watchdog timer (WDT) triggers a power-on
reset. Therefore, the USB may not operate properly after a power-on reset is triggered by
the WDT due to CPU runaway or a similar cause. (If a power-on reset is triggered by input
of a power-on reset signal from the RES pin, the USB registers are initialized and there is
no problem.) Consequently, an initialization routine should be used to write the initial
values listed below to the following three registers, thereby ensuring that all the USB
registers are properly initialized, immediately following a reset.
UCTLR = H'03, UIER3 = H'80, UIFR3 = H'00
14.8.9 EP0 Interrupt Sources Assignment
EP0 interrupt sources assigned to bits 3 to 0 in UIFR0 must be assigned to the same interrupt
signal (EXIRQx) by setting UISR0. There are no other restrictions on interrupt sources.