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a question on wakeup from standby | Cypress Semiconductor

a question on wakeup from standby

Summary: 1 Reply, Latest post by danaaknight on 14 Mar 2013 06:09 AM PDT
Verified Answers: 0
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tan999's picture
2 posts


I am using CY8C20346A, to save power, M8C standby is used, when a gpio interrupt come, M8C will be wakeup after for a while. in TRM "Wakeup Sequence" in page83, there are T0, T1, T2, T3, T4 points.

After wakeup, I need to use core/GPIO/I2C slave/capsence/timer0 modules,  can I start working after T0 or need to wait until T4?


user_14586677's picture
7646 posts

Looks like T4, from the TRM -


11.4.2 Wakeup Sequence

When asleep, the only event that wakes the system is an
interrupt. The Global Interrupt Enable of the CPU Flag regis-
ter does not need to be set. Any unmasked interrupt wakes
the system up. It is optional for the CPU to actually take the
interrupt after the wakeup sequence.

The wakeup sequence is synchronized to the taps from the
wakeup timer (running on IMO clock). This allows the flash
memory module enough time to power up before the CPU
asserts the first read access. Another reason for the delay is
to allow the IMO, bandgap, and LVD/POR circuits time to
settle before actually being used in the system. As shown in
Figure 11-2, the wakeup sequence is as follows.

1. The wakeup interrupt occurs and the sequence is initi-
ated at INT (shown in Figure 11-2 on page 83). The
interrupt asynchronously enables the regulator, the
bandgap circuit, LSO, POR, and the IMO. As the core
power ramps, the IMO starts to oscillate and the remain-
der of the sequence is timed with configurable durations
from the wakeup timer.
2. At T1, the bandgap is sampled and the flash is enabled.
3. At T2, the flash is put in power saving mode (idle).
4. At T3, the POR/LVD comparators are sampled and the
CPU restarts.


Regards, Dana.

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