USB334X datasheet(61/92 Pages) MICROCHIP

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DS00002646A-page 61

USB334x

6.7.2

USB AUDIO MODE (USB3341 and USB3346)

When the USB334x is powered in Synchronous Mode, the Audio switches can be enabled by asserting the SpkLeftEn,

or SpkRightEn bits in the Carkit Control register. After the register write is complete, the USB334x will immediately

enable or disable the audio switch. Then the Link can set the CarkitMode bit in the Interface Control register. The

SpkLeftEn, or SpkRightEn bits must be written before the CarkitMode bit.

After the CarkitMode bit is set, the ULPI interface will become redefined as described in Table 6-10.

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 5.7.1, "ID Resistor Detection," on page 32. If the USB334x is in ULPI mode, an RXCMD will be

generated with bit 6 low. If the USB334x is in Low Power Mode (or one of the other non-ULPI modes), the DATA[3] inter-

rupt signal will go high.

After the USB334x 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, "Vendor Rid Conversion," on page 74. 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.

6.8.1

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,"

on page 59. 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 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 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.

TABLE 6-12:

ULPI REGISTER PROGRAMMING EXAMPLE TO ENTER AUDIO MODE

R/W

Address

(HEX)

Value

(HEX)

Description

Result

Configure Non-Driving mode

OpMode=01

Enable Audio connections

SpkrRightEn=1, SpkrLeftEn=1

Enable carkit mode

CarkitMode=1

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