USB333X datasheet(57/85 Pages) MICROCHIP

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DS00001880A-page 57

USB333x

6.8

RID Converter Operation

The RID converter is designed to read the value of the ID resistance to ground and report back its value through the

ULPI interface.

When a resistor to ground is applied to the ID pin the state of the IdGnd comparator will change from a 1 to a 0 as

described in Section 5.6.1. If the USB333x is in ULPI mode, an RXCMD will be generated with bit 6 low. If the USB333x

is in Low Power Mode (or one of the other non-ULPI modes), the DATA[3] interrupt signal will go high.

After the USB333x 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 7.1.3.4. 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.

6.9

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 mode is provided as an alternate mode to the CarKit Mode defined in Section 6.7, "Carkit Mode".

In the CarKit mode the Link is unable to view the source of the interrupt on ID. For the Link to view the interrupt on ID

the PHY must be returned to synchronous mode so the interrupt can be read. This will force the audio switches to be

deactivated during the PHY start-up which may glitch the audio signals. In addition the Link can not change the resis-

tance 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 having to break the audio connection. The Headset Audio mode

also allows for the Link to change the resistance on the ID pin to change the audio device attached from mono to stereo.

Exiting Headset Audio Mode is the same as exiting Low Power Mode as described in Section 6.5.2. The RESETB pin

can also be pulsed low to reset the USB333x and return to Synchronous Mode.

TABLE 6-13:

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 Id_pullup330

must be enabled.

IdFloatRise

and IdFloatFall must be enabled.

IdPullup330

DATA[6]

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

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

the value shown in Table 4-9.

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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