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Put CPU to sleep but keep digital hardware running | Cypress Semiconductor

Put CPU to sleep but keep digital hardware running

Summary: 3 Replies, Latest post by mkap on 01 Apr 2010 11:00 AM PDT
Verified Answers: 0
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danieltrollhagen's picture
1 post

The data sheet of the CY8C38 family states that in an "Alternate Active Mode" it is possible to stop the CPU but keep the peripherals running.

Can someone please hint me how to achieve this? I found no possibility to configure power management from the Creator, nor a description which commands/registers must be used for sleep modes like on other processors.

I tried the CyWait() function from the CYLIB_POWER_MANAGEMENT, but this seems to stop the BUS_CLK which I need for the peripherals to operate.

lnat's picture
Cypress Employee
1 post

The Alternate Active mode is used to disable peripherals which are not required. Since the combination is very huge, we don't have an API to do it. The API CyWait will change the mode to Alternate Active. But before that you should decide which peripherals are required. That is done using the STANDBY registers. These registers start from location 0x43B0 and you can find then cydevice.h as CYDEV_PM_STBY_CFG0 etc. We have to use these registers to control which peripherals should be enabled. And then Cy_Wait should be called.

graa's picture
Cypress Employee
223 posts

So, if a peripheral is enabled using the STANDBY registers, will the BUS_CLK be active after CyWait is called?

mkap's picture
6 posts


Yes it will. All MHz frequency clocks are active in Alt. Active mode, unless otherwise specified by the user.


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