# CP2102 USB Suspend Question

I'm working with a CP2102. This has two USB suspend lines, suspend (pin 12) and suspend/ (pin 11). For pin 12, it says, "This pin is driven high when the CP2102 enters the USB suspend state." For pin 11, it says, "This pin is driven low when the CP2102 enters the USB suspend state." I am confused by the fact it has two suspend lines. Does this mean I need to observe both lines and enter sleep mode only when BOTH invert state and that transient states which do not imply USB suspension are possible? Or does this mean I can watch either pin, based on whichever logic I prefer (active high vs active low)? Basically, is this a logical boolean AND or a logical boolean OR for these lines?

Right now my plan is to simply tie one of these lines to one of the external interrupt pins on my uC. But if I need to observe both, I don't guess that will work unless I then tie the other line to a pin and perform a digitalRead to obtain its state. As I'm tight on pins, if possible, I'd certainly like to use only one of the two lines.

Silabs' CP2102 data sheet can be found here.

gerg: I'm working with a CP2102. This has two USB suspend lines, suspend (pin 12) and suspend/ (pin 11). For pin 12, it says, "This pin is driven high when the CP2102 enters the USB suspend state." For pin 11, it says, "This pin is driven low when the CP2102 enters the USB suspend state." I am confused by the fact it has two suspend lines. Does this mean I need to observe both lines and enter sleep mode only when BOTH invert state and that transient states which do not imply USB suspension are possible? Or does this mean I can watch either pin, based on whichever logic I prefer (active high vs active low)? Basically, is this a logical boolean AND or a logical boolean OR for these lines?

Right now my plan is to simply tie one of these lines to one of the external interrupt pins on my uC. But if I need to observe both, I don't guess that will work unless I then tie the other line to a pin and perform a digitalRead to obtain its state. As I'm tight on pins, if possible, I'd certainly like to use only one of the two lines.

Silabs' CP2102 data sheet can be found here.

It sounds to me that they just make avalible both an active high and active low output signal and allow you to pick the one that works best for your application. Just pick one and use it as you require.

Lefty

Thanks Lefty.

If you look at the block diagram, you can confirm retrolefty's comment. The diagram shows both outputs, one of them with an inverter.

You know I'd looked at that diagram several times and never once picked up on that. Good catch.

Thanks guys!