DG128 - Wait and Pseudo Stop mode current usages

[Donal]

Hello,
I'm having a bit of trouble with reducing the current consumption for my project.

I need to put the module into a low power mode where wake-up on CAN is enabled.

I've tested wake-up on CAN for both Wait and Pseudo-Stop mode, both work correctly.

However, my problem is with the current usages. When the module enters wait mode, the current drops from about 30mAmps to 12mAmps.

When entering stop mode, the current usage drops only to 22mAmps. Shouldn't this drop alit further?

Cheers,
Donal

[Alban]

Hi Donal,

Either your part does not enter in STOP mode or the current is not measured properly.

With WAIT you already observe a drop from 30mA to 12mA.

STOP halts all clocks and will be way below WAIT mode.

There is no way to get an S12 MCU consumption of 22mA in STOP mode.

The datasheet indicates STOP Currents for each MCU.

I would advise you make sure you enter STOP mode properly. There are Application Notes available and I think a few of Freescale Technology Forum presentations explains the steps to follow. Look for 2005 presentation in Florida.

BUT in STOP, msCAN is stopped !!! Check with the msCAN12 datasheet: as all clocks are stopped, you need time for the crystal to go back to the right frequency, during this time you don't have any precised clock and will lose a frame.

Cheers,

Alban.

[Donal]

Hi Alban,
Also, just to confirm with you that the module can wake-up on CAN when the module is in STOP mode and the wake-up on CAN has been enabled? But as you said, the first message is used to wake up the module and some subsequent messages may not be received as the oscillator isn't ready for about 2.5ms (16Mhz in pierce circuit).
Cheers,
Donal

[Alban]

Sorry Donal, I don't understand the question

The CAN transceiver will probably generate an asynchronous interrupt somewhere to wake-up the beast.

Not sure and don't have too much time to look just now.

[Donal]

Hi Alban,
Cheers for the info!.
Much appreciated.
Donal

[Donal]

Hi Alban,
Cheers for the info.

Do you know the location of the FTF presentation that describes the steps to follow.
I've had a look, but can't seem to find any presentations for 2005!

Cheers,
Donal

[Alban]

Hi,

Low-Power Techniques for the S12X Family | pdf
AN3289 discusses how to combine S12X features to obtain greater performace at minimum power levels. It also identifies best practices when creating hardware.

S12X low power app note - 16-Bit Microcontrollers - Freescale Forums | html
... low power features of the devices. Look for AN3289 or click here. Steve 2006-07-14 06:58 AM Add ...

Cheers,

Alban

Message Edited by Alban on 2006-09-06 03:03 PM