USB5926C datasheet(44/65 Pages) MICROCHIP

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2019 - 2021 Microchip Technology Inc.

DS00003190B-page 44

USB5926C

If the above example instead uses a notebook that doesn’t support DP over USB-C, then the alternate mode negotiation

will fail. The docking station will not have a way to enable the DP monitor capability, reducing functionality for the cus-

tomer. For this is the reason, USB Billboard capability is mandated. In this case, a USB Billboard device class endpoint

must appear on a hub port within the Docking Station, and it must provide text and or a web site link which will provide

information to the user regarding the corrective steps required to use the feature.

In the case of the USB5926C, all of the above mentioned negotiation capability will occur outside of the USB5926C via

an external USB Power Delivery capable device that contains a full USB PD stack and can communicate via USB PD

messaging. In an alternate mode failure case, the USB5926C will provide that message by allowing the USB host to

enumerate an internal USB Billboard Device Class just after the failure in response to a signal from the external USB

PD controller. The Billboard Device descriptors will contain the failure message to the USB Host. The message itself will

be prerecorded in the device’s OTP memory.

8.8.1

BILLBOARD ENABLE IN OTP AND

GPIOx PIN USE

Any of the

GPIOx pins may be selected to use as the BILLBOARD_EN input. By default, GPIO68 is selected when the

Billboard feature is enabled.

The

BILLBOARD_EN input signal is active low. When the pin is driven low by a Power Delivery controller to indicate

an alternate mode negotiation failure, the Billboard functionality will activate.

TABLE 8-10: USB BILLBOARD CONTROL

USBBILLBOARDCNTL

(OTP ADDR4 - RESET=0X14)

USB BILLBOARD CONTROL

BIT

NAME

R/W

DESCRIPTION

[7:6]

Reserved

R/W

Always read ‘0’

[5:1]

BILLBOARD_EN Pin

Select

R/W

00000=

GPIO64

00001=

GPIO1

00010=

GPIO2

00011=

GPIO3

00100=

GPIO65

00101=

GPIO66

00110=

GPIO67

00111=

GPIO23

01000=

GPIO10

01001= Reserved

01010=

GPIO68 (default)

01011=

GPIO6

01100=

GPIO69

01101=

GPIO70

01110=

GPIO71

01111=

GPIO5

10000=

GPIO4

[0]

Billboard Support Enable

R/W

0 = Billboard support disabled

1 = Billboard support enabled

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