DF2211NP24V Renesas Technology / Hitachi Semiconductor, DF2211NP24V Datasheet - Page 534

• Manufacturer Part Number: DF2211NP24V
• Description: H8S/2200 Series, 2212 Group, USB, RTC, HSS TNP-64B; Vcc= 2.7 to 3.6 volts, Temp= -20 to 75 C; Package: PVQN0064LB-A
• Manufacturer: Renesas Technology / Hitachi Semiconductor

Section 14 Universal Serial Bus (USB)
14.3.16 USB Interrupt Flag Register 0 (UIFR0)
UIFR0 is an interrupt flag register indicating the setup command reception, EP0 and EP3
transmission/reception, and bus reset state. If the corresponding bit is set to 1, the corresponding
EXIRQ0 or EXIRQ1 interrupt is requested to the CPU. A bit in this register can be cleared by
writing 0 to it. Writing 1 to a bit is invalid and causes no operation. Consequently, to clear a flag,
write 0 to the corresponding bit and 1 to all the other bits. (For example, write H'DF to clear bit 5.)
The bit-clear instruction is a read/modify/write instruction, so if a new flag is set between the read
and write operations, there is a danger that it may be cleared erroneously. Therefore, do not use the
bit-clear instruction to clear bits in this interrupt flag resister.
Rev.7.00 Dec. 24, 2008 Page 480 of 698
REJ09B0074-0700