AS0260CSSC28SUD20 datasheet(49/83 Pages) ONSEMI

49 / 83 page

AS0260 DS Rev. G Pub. 5/15 EN

©Semiconductor Components Industries, LLC, 2015.

AS0260: 1/6-Inch 1080P High-Definition (HD) System-On-A-Chip (SOC) Digi-

tal Image Sensor

UVC Interface

The AS0260 supports a set of UVC (USB Video Class) controls, in order to simplify the

integration of the AS0260 with a host's USB bridge (or ISP) device.

The AS0260 firmware includes a 'UVC Control' component that augments the CamCon-

trol variables. The UVC Control component sits above the CamControl interface (in

terms of abstraction) and acts as a 'virtual host'. The intention is that CamControl and

all other components are unaware of the UVC Control component.

UVC Control exposes a new 'UVC control' page of shared variables to the host. This page

contains variables compliant with the UVC 1.1 specification (where possible). The vari-

ables on this page are named to match the UVC specification, and have matching data

sizes, units and ranges as required. Each UVC variable is 'virtual' - it does not control any

AS0260 function directly.

AS0260 therefore provides a 'dual-personality' host interface:

The primary CamControl interface, this interface exposes the full feature-set of the

device.

The secondary UVC Control interface, which simplifies integration of AS0260 into a PC-

Cam application.

Constraints

There are a number of constraints imposed on the host in order to simplify the imple-

mentation of the UVC feature; the following sections will detail the limitations.

No Simultaneous Operation There is a constraint that these two interfaces should not

be used by the host simultaneously. The assumption is that the host will use the

CamControl interface at start-up to configure the part as desired. The host can then

continue to use the CamControl interface, or it can use the UVC Control interface. The

reason for this constraint is that as stated earlier, the UVC Control component acts as a

virtual host - the other firmware components do not know of its existence. UVC Control

modifies selected CamControl variables in order to control the AS0260.

No Coherency The AS0260 cannot guarantee coherency between the UVC Control

interface and the CamControl interface. The value of variables on the UVC Control page

may only reflect the last change made by the host (or the default value) - there is no

immediate coherency between a UVC Control variable and its equivalent CamControl

counterpart.

For example, suppose the host sets the desired scene brightness via the UVC Control

page. The AS0260 then sets the target brightness via the CamControl page. Reading the

current desired brightness on the UVC Control will return the original UVC value, not

the actual value being used by the AS0260.

Note however that the converse is not true; changes to UVC Control variables are

reflected in the CamControl Control variables, because the UVC Control feature acts as a

virtual host - it modifies the CamControl variables itself.

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