TC1796
Peripheral Units (Vol. 2 of 2)
Analog-to-Digital Converter (ADC)
User’s Manual
25-31
V2.0, 2007-07
ADC, V2.0
The arbitration participation flag can also be cleared under software control. Writing a 0
to the corresponding flag clears the arbitration participation flag. All bits in the
corresponding conversion request pending register are cleared if a participation flag of
a parallel source is cleared under software control. If a participation flag of a sequential
source is cleared, the following action is performed:
•
ONLY
the request bit of the back-up register is cleared,
if the back-up register
contains valid data
. The request bit of the corresponding conversion request
register (CHIN or QUEUE0) is
not
cleared in this case.
•
OR
the request bit of the corresponding conversion request register (CHIN or
QUEUE0) is cleared,
if the backup register does not contain valid data
.
Note: Writing a 1 to a participation bit has no effect.
25.1.3.3 Cancel Functionality
Channel Injection and Synchronized Injection have the ability to cancel a currently
running conversion. If a conversion is cancelled, one of the following actions are
performed:
•
If a conversion initiated by a parallel source is cancelled, the conversion request flag
is automatically set again in the corresponding conversion request pending register.
•
If a conversion initiated by a sequential source is cancelled, the control information
(such as resolution, external multiplexer information, etc.) of the cancelled
conversion is rescued into the backup register (for example: queue based conversion
is cancelled, so the queue backup register receives the control information of the
cancelled conversion).
Afterwards, the request participates in the arbitration anew and will be served according
to its source-arbitration level.
25.1.3.4 Clear of Pending Conversion Requests
This feature can be used to save conversion time by handling more than one conversion
request at the same time.
Clear of Pending Conversion Requests in Parallel Sources
If several conversion requests are pending for the same analog channel and a
conversion for this analog channel has been started, all pending conversion requests of
parallel
sources can be cancelled for this analog channel by the arbiter (CON.CPR = 1).
For example, if timer, software and auto-scan trigger a conversion request for the same
analog channel, only one conversion is started for this analog channel. The other two
pending conversion requests will be automatically cancelled by the arbiter. Note that the
conversion will be started for the arbitration winner, the source with the highest priority.
The conversion result is valid for all parallel sources which requested this channel. A
service request is generated only for the source that caused the processed conversion.