PORTS Forum

Ports and Interfaces => USB => Topic started by: stevop123 on January 11, 2016, 11:06:51 am

Title: usb type c cables
Post by: stevop123 on January 11, 2016, 11:06:51 am

Hi Jan,

I was looking over the usb type c specification.  Is it correct that all Type-C to Type-C cables must support USB 3.1 SuperSpeedPlus?
They way I read it is that passive USB 3.0 Type C to Type C cable is not allowed.  Am I correct?

Also, is it possible to have a passive usb 3.1 Type C to Type C cable?  It looks to me that only a passive USB 2.0 Type C to Type C is allowed.
Therefore, all usb 3.1 type C to type C cables are active and marked cables.  Is that correct?

BTW, I enjoyed your book.

Thanks,

Stephen

P.S. - Do you have more information on Debug Accessory Mode?  What is it?  How is it used.

Title: Re: usb type c cables
Post by: Jan Axelson on January 11, 2016, 02:21:30 pm

If I recall correctly, the Type-C developers decided not to define a USB 3.0 Type-C cable because it would just add to the clutter of options and would provide no benefit. You can use a USB 3.1 cable on USB 3.0 hardware.

As I understand it, most cables are passive as defined in the Type-C spec. From 1.5, a passive cable is:

A cable that does not incorporate any electronics to condition the data path signals. A passive cable may or may not be electronically marked.

And from 4.9:

An active cable is an electronically marked cable that incorporates data bus signal conditioning circuits, for example to allow for implementing longer cables.

If you mean "not electronically marked," 4.9 says:

All USB Full-Featured Type-C cables shall be electronically marked. USB 2.0 Type-C cables may be electronically marked.

I'm glad to hear you enjoyed USB Complete!

Title: Re: usb type c cables
Post by: Rajaram Regupathy on January 19, 2016, 12:18:44 am

> P.S. - Do you have more information on Debug Accessory Mode?  What is it?  How is it used.

Debug Accessory mode is a specification that is evolving similar to Audio Accessory mode.These two are special cases where in which a Type-C device type (non USB) is established without the power delivery alternate mode protocol and Type-C lines are used for audio/debug device.

These device types are established by presenting appropriate resistance on the CC lines. For ex: Ra & Ra for Audio and Rd & Rd for Debug accessory

>Also, is it possible to have a passive usb 3.1 Type C to Type C cable?  It looks to me that only a passive USB 2.0 Type C to Type C is allowed.
>Therefore, all usb 3.1 type C to type C cables are active and marked cables.  Is that correct?

Yes passive(but marked) 3.1 Type-C to Type-C cable is possible. Please note a passive  cable can be marked or un marked. Active cables are marked.  here passive means no signal conditioning

HTH