Holding an SX in Reset

Zoot

I have a project where an SX pin controls the enable line of a 5v 2A regulator (allowing the micro to turn power on/off to the subsystems). The enable line has a pulldown so that when the SX is off or in reset, the line is hold low (power off) and is only brought high (power-on) when the SX pin is an output and high.

I want to save some wiring and party-line setup back to the main host, because the host also needs to be able to shut power down to the subsystem. So my thought is just to let the host reset the SX and hold it there when it needs to (which would also make the enable line an input and let it be pulled low). The host needs to be able to reset the SX anyway.

Is there any reason not to let the host hold the SX in reset for an extended time? I'm talking minutes or half-hours, not days or weeks. Also, does the SX use less power when held in reset?

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pjv

Zoot;

Regarding power consumption during RESET, there is probably not much saving as the SX clock continues to run while the RESET is low, so all that is gained is non-clocking of the logic.

Cheers,

Peter (pjv)

Bean

I should not be a problem. Just remember that it takes the SX about 18mSec to startup after reset goes high.

Bean.

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Zoot

Thanks. In this case that's fine -- the reason that the host would reset the SX and or cycle the power is because of catastrophic loss of control of motors on a 70lb 'bot -- the startup and init routines in the host take several seconds, and it waits on a reply from the SX before proceeding anyway.

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$WMc%

Zoot

Sounds Like You have a Cool project. 70lbs,

Cool Dude!

___________$WMc%_____________

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Ugha

I'm just curious... why did you decide to hold the SX in reset instead of using sleep and a port B edge-detection?

Zoot

Ugha -- my purpose here *is* resetting the SX. Under certain circumstances the host may need to reset the SX; I merely wanted to piggy back the power-cycling as part of the reset so I don't have to use 3 pins on the host (one for serial rx/tx, one for reset, one to cycle power to the peripheral board). There is no case where the host would reset the SX and wouldn't also power-cycle the motor driver. But the SX may be held in reset for a bit while the host initializes all it's systems, gets ready to move, etc.

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When the going gets weird, the weird turn pro. -- HST

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Ugha

Oh... I'm sorry. I thought that using the MIWU pins would bring it out of sleep AND cause a reset.

Please excuse the newbieness [noparse]:)[/noparse]