PORTS Forum

Ports and Interfaces => USB => Topic started by: yalect on March 23, 2014, 07:57:20 am

Title: usb function
Post by: yalect on March 23, 2014, 07:57:20 am

thank you Mr Jan Axelson for Previous replys, I understand that each of D+ and D- works like out or in for type of transfer from begining at numeration, will not change after, and which Usually of them is in and other is out ?
thank you

Title: Re: usb function
Post by: Jan Axelson on March 23, 2014, 12:23:45 pm

No, low, full, and high speeds all use differential signaling. Differential zero is when D+ is logic low and D- is logic high as defined by the USB 2.0 spec. Differential one is when D+ is logic high and D- is logic low as defined by the USB 2.0 spec. Data travels in one direction at a time.

See 7.1.7 in the USB 2.0 spec.

Title: Re: usb function
Post by: yalect on March 26, 2014, 04:13:06 am

Hi, you mean we can't use term of in and out for D+ or D- or clearly (Pin in) and (Pin out) not standard for example for usb 2.0 or I can say Dout and Din ?
many thank

Title: Re: usb function
Post by: Jan Axelson on March 26, 2014, 10:18:39 am

No, Dout and Din are not accurate descriptions. Both lines carry data in both directions.

Title: Re: usb function
Post by: yalect on April 16, 2014, 07:27:02 am

I understood that after numeration of device, D+ can works in and out data together and the same for D- or each one can works in direction ( during operating of  one device)   
regards

Title: Re: usb function
Post by: Jan Axelson on April 16, 2014, 09:23:17 am

This might help in understanding how the interface works:

http://en.wikipedia.org/wiki/Differential_signaling