LS1043A, Asleep Query

[logeshs]

Hi,

In LS1043A reference schematics Asleep pin is used as Reset Configuration pin (please find the attachment). Do we need to configure Asleep pin for any particular function during boot up? What are the functions of Asleep pin? Please confirm what should we want to do with that pin.

Thanks

[alexander_yakov]

ASLEEP is used to indicate that the processor is in sleep mode (LPM20) state. If this output is not necessary in your design, than you can conigure this pin as GPIO. Note that this pin works as ASLEEP at reset, this must be taken into account when using this pin as GPIO.

Have a great day,
Alexander

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[logeshs]

Hi,

Thanks for reply.

In Reference schematics it is mentioned as "cfg_xvdd_sel" Does anyway this pin is related to this configuration? Also kindly request you to confirm why "cfg_xvdd_sel" is given in the Asleep net?

Thanks.

[alexander_yakov]

Yes, LS1043A Device Datasheet also states this pin is reset configuration pin (see Table 1, reference to note 4).

However, there is no information about this pin in Reference Manual, Section "4.4.5 Power-on reset configuration".

This means this configuration pin is reserved for further use, please do not drive this pin externally at reset.

The following is said in LS1043A Design Checklist (application note AN5012):

This pin is a reset configuration pin. It has a weak (~20 kΩ) internal
pull-up P-FET that is enabled only when the processor is in its reset
state. This pull-up is designed such that it can be over powered by an
external 4.7 kΩ resistor. However, if the signal is intended to be high
after reset, and if there is any device on the net that might pull down
the value of the net at reset, a pull-up or active driver is needed.

This document is available for download from the LS1043A documentation page:

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