TC1796
Peripheral Units (Vol. 2 of 2)
Analog-to-Digital Converter (ADC)
User’s Manual
25-6
V2.0, 2007-07
ADC, V2.0
channel. If all pending conversion requests are processed, the arbitration participation
flag of this parallel source is cleared.
The bits of the conversion request pending register can be cleared globally under
software control by clearing the arbitration participation flag for this source.
25.1.2.2 Sequential Conversion Request Sources
Sequential conversion request sources generate only one conversion request at a time
for an analog channel. The settings for this conversion are derived from the control
register of the sequential source.
shows the available sequential conversion
request sources including the associated control and status blocks.
A sequential conversion request source consists of a control register, a back-up register,
an arbitration participation flag, and the source arbitration level.
Each sequential conversion control register contains a conversion request bit, the
channel number to be converted, two control bits for the external multiplexer settings,
one bit for the analog input channel group selection, and control information to select the
resolution of the channel. Setting the conversion request bit causes the arbitration
participation flag to be set. This informs the arbiter to include the sequential conversion
request source into arbitration. If this sequential source is the arbitration winner, a
conversion is started for the analog channel specified within the request register. The
settings of the external multiplexer and the resolution of the ADC are also derived from
this conversion request control register.
Starting a conversion causes the conversion request bit to be cleared by the arbiter. The
arbitration participation flag is automatically cleared if the conversion request register
and the back-up register contains no valid request.
If a currently running conversion initiated by a sequential source is cancelled, the arbiter
restores the conversion information (conversion request bit, external multiplexer setting,
analog input channel group selection, conversion resolution) in the back-up registers for
this channel. If the back-up register contains valid conversion information, the arbiter
reads from the back-up register instead from the conversion request control register.
Thus, the previously cancelled conversion participates in arbitration again. A new
Table 25-2
Sequential Conversion Request Sources
Request
Source
Control
Register
Back-Up
Register
Arbitration
Participation
Flag
Source
Arbitration
Level
Channel
Injection
CHIN
not accessible
via Bus
AP.CHP
SAL.SALCHIN
Queue
QR
not accessible
via Bus
AP.QP
SAL.SALQ