TC1784
Analog to Digital Converter (ADC)
User´s Manual
23-118
V1.1, 2011-05
ADC, V1.3
23.2.20
Equidistant Sampling
Each ADC kernel supports equidistant sampling of one (or more) analog input channels,
e.g. for audio purposes or digital filters.
Therefore, each request source can be programmed to take part in the arbitration round
and to win the arbitration (depending on the programmed priority levels), but without
starting the conversion immediately. The exact start point of the conversion is given by
a control signal (generated outside the ADC module, e.g. by a timer module) that is
selected as trigger input REQTRx of request source x. Equidistant sampling is ensured
if the REQTRx signal is generated synchronously to the arbiter timing, mainly for the
arbiter. Each ADC kernel provides an output ARBCNT, that is activated once per
arbitration round to count the arbiter cycles as timing base for the equidistant sampling
by a timer located outside the ADC module.
A requested equidistant conversion can start its sampling phase if the converter is idle
and the arbiter has decided which channel to convert. To ensure that the converter is
idle, the arbiter decides which channel to convert (winner of the arbitration round), but it
waits for the timer control signal to really start the measurement (preface time). If the
request source selected for equidistant sampling has been programmed with the highest
priority, no other request source can disturb the equidistant sampling.
The interpretation of the trigger signal REQTRx for equidistant sampling is enabled by
selecting timer mode in the corresponding request source input register
(RSIRx.TMEN = 1). The frequency of signal REQTRx defines the sampling rate and its
high time defines the length of the preface time interval where the corresponding request
source takes part in the arbitration. During the preface time, the currently running
conversion can be finished. It has to be programmed to a value allowing the converter to
become idle.
If signal ARBCNT is used as counting input signal for a timer, the arbiter has to be
programmed to run permanently (GLOBCTR.ARBM = 0). If the timer has an
independent time base, the arbiter can be stopped while no requests are pending. The
preface time has to be longer than one arbitration round.
Depending on the request source requesting equidistant sampling, one or more
channels can be converted one after the other. The order of the requested channels
being fixed by the request source, the equidistant sampling is also supported for several
channels. It is also possible to do equidistant sampling for more than one request source
in parallel if the preface times and the equidistant conversions do not overlap.
Summary of Contents for TC1784
Page 1: ...User s Manual V1 1 2011 05 Microcontrollers TC1784 32 Bit Single Chip Microcontroller ...
Page 3: ...User s Manual V1 1 2011 05 Microcontrollers TC1784 32 Bit Single Chip Microcontroller ...
Page 950: ...TC1784 Direct Memory Access Controller DMA User s Manual 11 132 V1 1 2011 05 DMA V3 03 ...
Page 1949: ...TC1784 General Purpose Timer Array GPTA v5 User s Manual 21 297 V1 1 2011 05 GPTA v5 V1 14 ...
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