RA8806
Preliminary Version 1.0
Two Layers Character/Graphic LCD Controller
6-7-4 Sleep Mode
The RA8806 provide two operation modes: Normal mode and Sleep mode. Please refer to Chapter
5 “Register Description” for Register WLCR explanation. RA8806 will shut down the system clock, to
achieve the minimum power consumption. When RA8806 is under the Sleep mode, only the status
register can be read, other registers are not allowed to read. Other command besides REG[00h] Bit-
7(Sleep mode) can’t be written. When RA8806 is under Sleep Mode, it can accept the following
three methods to wake-up.
1. Write REG[00h] Bit-7 = 0, then it will return to Normal Mode.
2. Touch event is detected.
3. Key-Scan is detected.
When RA8806 quit from Sleep mode, to avoid the incorrect activity, RA8806 must de-bounce the
wake-up event for enough time(about 1,000 system clock periods) to make sure it, then quit from
Sleep mode.
Besides, when MPU program RA8806 to enter Sleep mode, RA8806 can’t receive command from
MPU anymore till quit the Sleep mode. The command will be lost. User program must avoid the
possibility of the condition. For example, if RA8806 be programmed to Sleep mode, at the same
time, the MPU receives an external interrupt, and cause the MPU enter the Interrupt Service
Routine(ISR). That will cause RA8806 can’t correctly receive and recognize the command.
From the view of hardware design, the condition can’t be prevented. Because the external interrupt
is an individual mechanism of MPU. We can’t predicate the happen of it from the role of RA8806. It’s
a possible risk even the possibility is rare.
So it’s suggested that MPU must be mask the interrupt for RA8806 before commanding the RA8806
to enter the Sleep mode. The interrupt mask is off after RA8806 quit from Sleep mode. Besides,
because the status register can be read normally at Sleep mode. Also user can check the status in
the ISR for judgment. If RA8806 is checked under Sleep mode, MPU can quit ISR and execute
nothing to prevent incorrect activity.
Table 6-19
Reg.
Bit_Num
Description
Reference
Normal mode and Sleep mode
selection.
WLCR
Bit 7
REG[00h]
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