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TUSB322I

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SLLSEO5C – OCTOBER 2015 – REVISED MAY 2017

Product Folder Links: TUSB322I

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Copyright © 2015–2017, Texas Instruments Incorporated

7.3.2.3 Dual Role Port (DRP)

The TUSB322I default operation is a dual-role port controller. As a DRP, the TUSB322I can operate as a UFP

(sink) or a DFP (source). In DFP mode, the TUSB322I toggles between presenting as a DFP (Rp on both CC

pins) and presenting as a UFP (Rd on both CC pins).

When presenting as a DFP, the TUSB322I monitors the voltage level on the CC pins looking for the Rd

termination of a UFP. When a UFP is detected and TUSB322I is in the Attached.SRC state, the TUSB322I will

pull the ID pin low to indicate to the system the port is attached to a sink (UFP). Additionally, when a UFP is

detected, the TUSB322I will supply VCONN on the unconnected CC pin if Ra is also detected. In DFP mode, the

TUSB322I will initially advertise default USB Type-C current. The Type-C Current can be adjusted through I2C if

the system wishes to increase the amount advertised. TUSB322I will adjust the Rps to match the desired Type-C

Current advertisement. In GPIO mode, the TUSB322I will only advertise default Type C current.

When presenting as a UFP, the TUSB322I monitors the CC pins for the voltage level corresponding to the Type-

C mode current advertisement by the connected DFP. The TUSB322I will debounce the CC pins and wait for

VBUS detection before successfully attaching. As a UFP, the TUSB322I will detect and communicate the DFP’s

advertised current level to the system through the OUT1 and OUT2 GPIOs (if in GPIO mode) or through the I2C

CURRENT_MODE_DETECT register once in the Attached.SNK state.

The TUSB322I supports two optional Type-C DRP features called Try.SRC and Try.SNK. Products supporting

dual-role functionality can have a requirement to be a source (DFP) or a sink (UFP) when connected to another

dual-role capable product. For example, a dual-role capable notebook can be used as a source when connected

to a tablet, or a cell phone could be a sink when connected to a notebook or tablet. When standard DRP

products (products which don’t support either Try.SRC or Try.SNK) are connected together, the role (UFP or

DFP) outcome is not predetermined. These two optional DRP features provide a means for dual-role capable

products to connect to another dual-role capable product in the role desired. Try.SRC and Try.SNK are only

available when TUSB322I is configured in I2C mode. When operating in GPIO mode, the TUSB322I will always

operate as a standard DRP.

The Try.SRC feature of the TUSB322I device provides a means for a DRP product to connect as a DFP when

connected to another DRP product that doesn’t implement Try.SRC. When two products which implement

Try.SRC are connected together, the role outcome of either UFP or DFP is the same as a standard DRP.

Try.SRC is enabled by changing I2C register SOURCE_PREF to 2’b11. Once the register is changed to 2’b11,

the TUSB322I will always attempt to connect as a DFP when attached to another DRP capable device.

7.3.3 Type-C Current Mode

When a valid cable detection and attach have been completed, the DFP has the option to advertise the level of

Type-C current a UFP can sink. The default current advertisement for the TUSB322I device is 500 mA (for

USB2.0) or 900 mA (for USB3.1). If a higher level of current is available, the I2C registers can be written to

provide medium current at 1.5 A or high current at 3 A. When the CURRENT_MODE_ADVERTISE register has

been written to advertise higher than default current, the DFP adjusts the Rps for the specified current level. If a

DFP advertises 3 A, it ensures that the VDD of the TUSB322I device is 3.5 V or greater. Table 2 lists the Type-C

current advertisements in GPIO an I2C modes.

Table 2. Type-C Current Advertisement for GPIO and I2C Modes

TYPE-C CURRENT

GPIO MODE (ADDR PIN IN NC)

I2C MODE (ADDR PIN H, L)

UFP IN DRP MODE

DFP IN DRP MODE

UFP

DFP

Default

500 mA

(USB2.0)

900 mA

(USB3.1)

Current mode detected

and output through OUT1

/ OUT2

Only advertisement

Current mode detected

and read through I2C

register

I2C register default is 500

or 900 mA

Medium - 1.5 A

N/A

Advertisement selected

through writing I2C

register

High - 3 A

7.3.4 Accessory Support

The TUSB322I device supports audio and debug accessories in UFP, DFP mode and DRP mode. Audio and

debug accessory support is provided through reading of I2C registers. Audio accessory is also supported through

GPIO mode with INT_N/OUT3 pin (audio accessory is detected when INT_N/OUT3 pin is low).