Carrol Touch TouchSystems CarrollTouch Prog, Руководство программиста

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Chapter 5 - Smart-Frame Protocol II CARROLL TOUCH
5-10 Touch System Programmer’s Guide
follows the header, read the number of bytes specified by the byte count
(the report packet), and verify that the following byte is a trailer byte.
If the segment of the incoming byte stream under consideration fits this
format, the segment is deemed to be a valid SFP-II report packet and
the command error status, report number, and parameters are forwarded
to the interpretation layer.
Interpretation Layer
The format for SFP-II reports at the interpretation layer is as follows:
commanderrorstatus reportnumber
optionalreportparameters
To interpret the report, the host should first examine the command error
status parameter. If the command error status parameter indicates an
error, the host should take the appropriate action.
The host should then examine the report number. If the report number
does not correspond to a defined SFP-II report, the host should deem
the report invalid.
Finally, the host should examine the report to determine that the
appropriate number of parameter bytes for the report is present. If the
appropriate number is not present, or one or more of the parameter
bytes are otherwise invalid for the report (parameter is out of range and
so forth), the host should deem the report invalid.
If the host determines that all information in the interpretation layer is
valid, the host should process the command.
The bytes within the report packet are indexed beginning at 0 for the
SFP-II report number, and ending at (report packet byte count - 1) for
the last parameter byte. The length of the report packet is given by the
packet byte count that was read during the validation layer.
Example
An example of a report issued in response to a valid SFP-II command,
GetProtocolVersion (command 65), is:
E0 04 00 65 02 12 FF
E0
and
FF
are the header and footer, respectively.
04
indicates the
report contains four bytes.
00
is the command error status (Cmderr)
and indicates the report is valid.
65
is the report number, which is the