Sequencing - Texas Instruments UCD3138 Technical Reference Manual

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8.8

Sequencing

The ADC12 FSM can "auto-sequence" up to 16 conversions of any combination of ADC channels in a
single sequence configuration. The result of each conversion is stored into 16 ADC result registers,
representing the raw ADC data. The desired ADC channel for each sequenced conversion is programmed
into the ADC sequence select registers. Any of the 16 ADC channels can be programmed into one of the
conversion slots configured by the ADC Sequence Select Registers. Also, it is possible to program the
same ADC channel into multiple or all of the conversion slots for a given sequence. The conversion
sequence always starts with the programmed ADC channel in ADC Sequence Select Register 0 (Bits 3:0).
Conversions will continue until the configured number of maximum conversions is reached.
The sequencer can be triggered by the firmware or through a multitude of external trigger sources. The
external trigger sources include the rising edge of any DPWM output, any of the 7 Analog Comparator
results or the external ADC_EXT_TRIG pin (allowing trigger from off device). Additionally, the sequencer
can be configured to perform a single sequence or continually start the sequence of the external trigger
source. The sequencer can also be enabled to generate an interrupt to the embedded processor at the
end of a sequence.
The start of the sequencer can be delayed from the receipt of an external trigger. A counter within the
ADC12 Control Finite State Machine will delay the start of the sequence based on a programmable delay
configured by firmware. After the delay, the sequencer will start the conversions. For example, in order to
initiate a sequence of measurements 128nS after the ADC_EXT_TRIG pin trips, the following setting
should be applied.
AdcRegs.ADCCTRL.bit.EXT_TRIG_SEL = 8;
AdcRegs.ADCCTRL.bit.EXT_TRIG_DLY = 8;
AdcRegs.ADCCTRL.bit.EXT_TRIG_EN = 1;
Channel Mapping - The ADC12 is utilized to measure both internal and external voltage signals. The 16
inputs to the ADC12 block are referred to by channel numbers. 14 of the ADC Channels are connected to
external pins. The remaining 2 channels are tied to an internal temperature sensor and an internal test
channel. The following table details the channel mapping utilized on UCD3138.
Channel Number
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
SNIU028A – February 2016 – Revised April 2016
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// ADC_EXT_TRIG pin triggers the conversion
// 8 times 16 ns delay after the pin toggling
// Enable ADC-12 triggering via external sources
Internal/External Signal
AD-00 GP Analog Input to ADC12
AD-01 GP Analog Input to ADC12
AD-02 GP Analog Input to ADC12
AD-03 GP Analog Input to ADC12
AD-04 GP Analog Input to ADC12
AD-05 GP Analog Input to ADC12
AD-06 GP Analog Input to ADC12
AD-07 GP Analog Input to ADC12
AD-08 GP Analog Input to ADC12
AD-09 GP Analog Input to ADC12
AD-10 GP Analog Input to ADC12
AD-11 GP Analog Input to ADC12
AD-12 GP Analog Input to ADC12
AD-13 GP Analog Input to ADC12
Temp Sensor Internal Temperature Sensor
Test Channel Internal Test Channel (Test Use Only)
Copyright © 2016, Texas Instruments Incorporated
Sequencing
Description
ADC12 Overview
303