Block descriptions

STUSB4710

10/34

DocID030499 Rev 4

3

Block descriptions

3.1

CC interface

The STUSB4710 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 lines interface block is used to:



Configure the termination mode on the CC pins relative to the power mode supported,

i.e. pull-up for source power role



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



Protect the CC pins against over voltage

The CC control logic block is used to:



Execute the Type-C FSM relative to the Type-C power mode supported



Determine the electrical state for each CC pins relative to the detected thresholds



transition from one state to another in the Type-C FSM



Detect and establish a valid source-to-sink connection



Determine the attached mode: source, accessory



Determine cable orientation to allow external routing of the USB super speed data



mode



Handle hardware faults

The CC control logic block implements the Type-

C FSM’s corresponding to source power

role with accessory support.

3.2

BMC

This block is the physical link between USB PD protocol layer and CC pin. In TX mode, it

converts the data into biphase mark coding (BMC), and drives the CC line to correct

voltages. In RX mode, it recovers BMC data from the CC line, and converts to baseband

signaling for the protocol layer.

3.3

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.

3.4

Policy engine

The policy engine implements the power negotiation with the connected device according

to its source role, it implements the state machine that controls protocol layer forming and

scheduling 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.