Function To Wake Up The Mcu From Standby Mode - Fujitsu F2MC-8FX Hardware Manual

22.7.2

Function to Wake up the MCU from Standby Mode

The wakeup function enables the I
watch mode.
Function to Wake Up the MCU from Standby Mode
2
The I C macro includes a function to wake up the MCU from standby mode. The function is enabled by
writing "1" to the IBCR00:WUE bit.
When the MCU is in stop/watch mode with the IBCR00:WUE bit containing "1", if a start condition is
detected on the I
interrupt request is generated to wake up the MCU from stop/watch mode.
• Set IBCR00:WUE to "1" immediately prior to setting the MCU to stop or watch mode. Similarly, clear
IBCR00:WUE (by writing "0") after the MCU wakes up from stop or watch mode so that I
can restart as soon as possible.
• The wakeup function only applies to the MCU stop and watch modes.
Note:
In PLL stop mode, a PLL oscillation stabilization wait time is required in addition to the oscillation
stabilization wait time. This causes a very long delay between the MCU waking up and
communications restarting.
Figure 22.7-7 Comparison of Normal I
SDA0
SCL0
IRQ by
IBCR00:WUF
Machine
Clock
2
C macro to be accessed while the MCU is in stop or
2
C bus, the wakeup interrupt request flag bit (IBCR00:WUF) is set to "1" and the wakeup
1 3
2
1 Set the IBCR00:WUE bit to "1" immediately before entering stop/watch mode and make sure that IBSR0:BB = 0.
2 Set the MCU to stop/watch mode and the machine clock stops.
3 Detect a start condition in stop/watch mode. IBCR00:WUF is set to 1 and a wakeup IRQ is generated. After the
oscillation stabilization wait time, the MCU wakes up and enters main clock mode.
4 Clear the IBCR00:WUE bit to "0" so that I
"0" to clear the wakeup interrupt.
5 To receive the data byte correctly, the SCL0 must be released in the first cycle after 100 μs (assuming a
minimum oscillation stabilization wait time of 100 μs) from the start of I
SDA0).
2
C Operation and Wakeup Operation
5
4
2
C can restart the normal operation, and clear the IBCR00:WUF bit to
2
C transmission (falling edge detection of
2
CHAPTER 22 I C
2
C operation
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