3

Description of features

3.1

CC interface

The STUSB4500 controls the connection to the configuration channel (CC) pins, CC1 and CC2, through two main

blocks: the CC line interface block and the CC control logic block.

The CC line interface block is used to:

•

Set pull-down termination mode on the CC pins

•

Monitor the CC pin voltage values related to the attachment detection thresholds

•

Protect the CC pins against overvoltage

The CC control logic block is used to:

•

Execute the Type-C FSM related to the sink power role with debug accessory support

•

Determine the electrical state for each CC pin related to the detected thresholds

•

to another in the Type-C FSM

•

Advertise a valid source-to-sink connection

•

Determine the attached device mode: source or debug accessory

•

Determine cable orientation to allow external routing of the USB data

•

•

Handle hardware faults

3.2

Power delivery blocks

3.2.1

Physical layer

The physical layer defines the signaling technology for USB power delivery. It is the physical link between CC pins

and protocol layer. In Tx mode, it receives packet data from the protocol layer, calculates and appends a CRC,

encodes the payload (i.e. packet data and CRC) and transmits the packet (i.e. preamble, SOP, payload, CRC and

EOP) using biphase mark coding (i.e. BMC) over CC pins. In Rx mode, it recovers the clock and the data, detects

the SOP, decodes the received data including the CRC, detects the EOP and validates the CRC.

3.2.2

Protocol layer

The protocol layer has the responsibility to manage the messages from/to the physical layer. It automatically

manages the protocol receive timeouts, the message counter, the retry counter and the GoodCRC messages.

It communicates with the internal policy engine.

3.2.3

Policy engine

The policy engine implements the power negotiation with the connected device according to its sink role. It

implements all state machines controlling the protocol layer that forms and schedules the messages.

The policy engine uses the protocol layer to send/receive messages.

The policy engine interprets the device policy manager’s input in order to implement policy for port and directs the

protocol layer to send appropriate messages.

3.2.4

Device policy manager

The device policy manager deals with the power capability request and change management. It operates

according to the decision algorithm described in the following section.

STUSB4500

Description of the features

DS12499 - Rev 2

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