USB3320 datasheet(48/70 Pages) MICROCHIP

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USB3320

DS00001792B-page 48

 2014-2015 Microchip Technology Inc.

After the USB3320 has detected the change of state on the ID pin, the RID converter can be used to determine the value

of ID resistance. To start a ID resistance measurement, the RidConversionStart bit is set in the Vendor Rid Conversion

The Link can use one of two methods to determine when the RID Conversion is complete. One method is polling the

RidConversionStart

bit as described in Section 7.1.3.3. The preferred method is to set the RidIntEn bit in the Vendor Rid

Conversion register. When RidIntEn is set, an RXCMD will be generated after the RID conversion is complete. As

described in Table 6-3, the alt_int bit of the RXCMD will be set.

After the RID Conversion is complete, the Link can read RidValue from the Vendor Rid Conversion register.

6.7

Headset Audio Mode

This mode is designed to allow a user to view the status of several signals while using an analog audio headset with a

USB connector. This feature, exclusive to Microchip, is provided as an alternate mode to the CarKit Mode defined in

Section 6.5. In the CarKit Mode, the Link is unable to view the source of the interrupt on ID, except by returning to syn-

chronous mode to read the ULPI registers. This forces the audio switches to be deactivated, and may glitch the audio

signals. In addition, the Link cannot change the resistance on the ID pin without starting up the PHY to access the ULPI

registers.

The Headset Audio Mode is entered by writing to the Headset Audio Mode register, and allows the Link access to the

state of the VBUS and ID pins during audio without glitching the audio connection. The Headset Audio mode also

enables the Link to change the resistance on the ID pin and to change the audio headset attached from mono to stereo.

The ULPI interface is redefined as shown in Table 6-10 when Headset Audio Mode is entered.

Exiting Headset Audio Mode is the same as exiting Low Power Mode as described in Section 6.3.2. The Link must

assert STP to signal the PHY to exit. When the PHY can accept a command, DIR is de-asserted and the PHY will wait

until the Link de-asserts STP to resume synchronous ULPI operation. The RESETB pin can also be pulsed low to reset

the USB3320 and return it to Synchronous Mode.

TABLE 6-10:

PIN DEFINITIONS IN HEADSET AUDIO MODE

Signal

Connected To

Direction

Description

SessVld

DATA[0]

OUT

Output of SessVld comparator

VbusVld

DATA[1]

OUT

Output of VbusVld Comparator (interrupt must be enabled)

IdGndDrv

DATA[2]

Drives ID pin to ground when asserted

0b: Not connected

1b: Connects ID to ground.

DATA[3]

OUT

Driven low

IdGround

DATA[4]

OUT

Asserted when the ID pin is grounded.

0b: ID pin is grounded

1b: ID pin is floating

IdFloat

DATA[5]

OUT

Asserted when the ID pin is floating. IdPullup or d_pullup330

must be enabled as shown below.

IdPullup330

DATA[6]

When enabled a 330kΩpullup is applied to the ID pin. This

bit will also change the trip point of the IdGnd comparator to

the value shown in Table 4-7.

0b: Disables the pull-up resistor

1b: Enables the pull-up resistor

IdPullup

DATA[7]

Connects the 100kΩ pull-up resistor from the ID pin to

VDD3.3

0b: Disables the pull-up resistor

1b: Enables the pull-up resistor

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