TPS65987D: USB-C PD Controller for systems where power and data roles are opposite

Hi Josko,

Josko M said:

However, I can't figure out, how is determined, whether one USB-C PD port is USB Communications capable, and which role the port has, device or host. 
Is this also negotiated over CC lines? 

All type-C connections initially in one of two ways, as a Data DFP and Power Source, or as a Data UFP and Power Sink. The initial connection is determined by pullup and pulldown resistors on the CC lines.

To obtain a port where the power roles are "opposite", USB-PD is required. CC line communication using the PD spec will negotiate data or power role swaps to enter these mixed port roles when possible.

Josko M said:

My question is, whether this information about USB Communications Capability is enclosed in every data sheets or TRM of power delivery controllers and how to search for the USB-C PD controller that supports this? 

There is not a good way to determine if the PD controller supports the bit outside of seeing support for USB communication in the datasheet.

Josko M said:

Is this information for example enclosed in 0x5F Data Status Register Bit Field Definitions for the TPS65987D? 

The Data Status register is a status register that describes the active contract. In this case, it only reports what USB speed the active connection is in, if it is one at all. It does not configure the USB Comms capable bit as it is a read only register.

For the TPS65987, the communication capable bit is directly set in the source PDO 1 field of the Transmit Source Capabilities register, and can be done through the GUI. It is bit 90 of that register.

Josko M said:

Since TPS65987D has the NRND status, is there any replacement for this part?

You may want to explore using the TPS25751. 

The USB Comms Capable bit for this part is actually bit 11 of the port config register90x28). The public TRM has the bit "reserved" but we are in the process of updating it to match the image below.

Thanks and Regards,

Chris

Hi Josko,

Josko M said:

So the bit 90 says that USB-C Port with "TPS65987" is capable to communicate over USB data lines. Is this enough?  I can't figure out, how the other side knows which data role the USB-C Port  has, Host or Device,  and whether the USB-C Port is USB2.0 capable only, USB3.0 only, or both? In which register is this defined? 

When acting as source, yes, bit 90 in TX Source caps indicates USB comms support.

When acting as sink, bit3 in autonegotiate sink (0x37) needs to be used.

Data role is determined by a couple things, and should be managed by the ports individually. On initial connect, the CC line termination for the ports determines the data role. The port with the RP pull up resistors is the data DFP, and the port with the RD pulldown resistors is the data UFP. For type-C only, data roles are limited to this initial connection. For Type-C PD, Data role swaps can be negotiated using the CC-line PD communication, and each port will keep track of the data roles that are negotiated.

Two of the first messages sent when USB-C PD communication begins is the source caps message(sent by the source) and the request message(sent by the sink).

The source caps message uses bit 90 in TX source caps to indicate if the source is capable of USB communications.

The request message uses bit 3 of autonegotiate sink to indicate if the sink is also capable of USB communications.

There are additional messages that can be sent to see the highest USB speed that each port supports, but these are not required to be used. The PD controllers do not directly interact with the USB data lines for data purposes, so it is up to the USB endpoints to enumerate.

Data role can be checked in the status register. If the additional data speed communication occurs, the data will be in the data status register. Please look through the device TRM for more information on the status registers.

Josko M said:

Actually the same question for the TPS25751: how the other side knows which data role the USB-C Port with TPS25751 has, Host or Device,  and whether the USB-C Port is USB2.0 capable only, USB3.0 only, or both? In which register is this defined? 

The TPS25751 uses the USB comms capable bit in the port configuration register (mentioned in an earlier response).

The TPS25751 does not support the usb data speed reporting. 

As a UFP, you can check the status register, USB host present field to see if the far end is USB communications capable

As a DFP, you can check the Active RDO contract -> USB Communication Capable field to see if the far end is USB communications capable.

Josko M said:

Is there any updates here regarding the reference desing? 

There are no updates regarding the reference design.

Josko M said:

and is USB2.0 communication capable as Device (UFP).

For USB 2.0 communication, you should only need to set and check the USB comms capable bit.