Carrol Touch TouchSystems CarrollTouch Prog, Programmer'S Manual

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Chapter 5 - Smart-Frame Protocol II CARROLL TOUCH
5-4 Touch System Programmer’s Guide
Modal Protocols
The SFP-II is implemented as a modal protocol, meaning that, even if
a touch system supports both the SFP and SFP-II, it can only support
one protocol at a time and, during that time, cannot accept commands
from the other protocol. To switch between protocols, use the
SwitchToSFP-II (65H) SFP command and the SwitchToClassicSFP
(64H) SFP-II function.
Note
The SFP-II protocol currently lacks many necessary features that
are supported in SFP, so it is necessary for the host to switch
between the SFP and SFP-II to access these features. When the
SFP-II protocol specification is complete, it will include all
necessary features, eliminating the need to switch protocols.
Backward Compatibility
Touch systems that implement SFP-II (known as SFP-II aware touch
systems) also implement the existing SFP to ensure backward
compatibility with existing touch systems and to avoid obsoleting the
installed base of touch applications. Backward compatibility means
that:
1. SFP-II aware touch systems may be used with existing
applications that use the SFP without requiring the application to
be modified.
This is possible because the initialization sequence is identical for
both SFP-II aware and non SFP-II aware touch systems, and
because SFP-II aware touch systems power up under SFP and
remain in SFP until explicitly commanded to switch to SFP-II.
2. Applications and drivers may be written to use both SFP-II aware
touch systems and non SFP-II aware touch systems (albeit with
reduced functionality).
This is possible because a mechanism exists whereby applications
and drivers can interrogate the touch system to determine whether
the touch system supports SFP-II. The application or driver may
choose to use the advanced functions of SFP-II or to use only the
SFP.