STR91XFA datasheet(29/78 Pages) STMICROELECTRONICS

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STR91xFA

Functional overview

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2.24

A/D converter (ADC) with DMA

The STR91xFA provides an eight-channel, 10-bit successive approximation analog-to-digital

converter. The ADC input pins are multiplexed with other functions on Port 4 as shown in

Table 5. Following are the major ADC features:

●

Fast conversion time, as low as 0.7 usec

●

Accuracy. Integral and differential non-linearity are typically within 4 conversion counts.

●

0 to 3.6V input range. External reference voltage input pin (AVREF) available on 128-pin

packages for better accuracy on low-voltage inputs. See Table 7: Operating conditions, for

restrictions to the relative voltage levels of VDDQ, AVDD, AVREF, and AVREF_AVDD.

●

CPU Firmware may convert one ADC input channel at a time, or it has the option to set the

ADC to automatically scan and convert all eight ADC input channels sequentially before

signalling an end-of-conversion

●

Automatic continuous conversion mode is available for any number of designated ADC

input channels

●

Analog watchdog mode provides automatic monitoring of any ADC input, comparing it

against two programmable voltage threshold values. The ADC unit will set a flag or it will

interrupt the CPU if the input voltage rises above the higher threshold, or drops below the

lower threshold.

●

The ADC unit goes to stand-by mode (very low-current consumption) after any reset event.

CPU firmware may also command the ADC unit to stand-by mode at any time.

●

ADC conversion can be started or triggered by software command as well as triggers from

Timer/Counter (TIM), Motor Controller and input from external pin.

2.24.1 DMA

A programmable DMA channel may be assigned by CPU firmware to service each ADC

conversion result for fast DMA single-transfer.

2.25

Standard timers (TIM) with DMA

The STR91xFA has four independent, free-running 16-bit timer/counter modules designated

TIM0, TIM1, TIM2, and TIM3. Each general purpose timer/counter can be configured by

firmware for a variety of tasks including; pulse width and frequency measurement (input

capture), generation of waveforms (output compare and PWM), event counting, delay timing,

and up/down counting.

Each of the four timer units have the following features:

●

16-bit free running timer/counter

●

Internal timer/counter clock source from a programmable 8-bit prescale of the CCU PCLK

clock output

●

Optional external timer/counter clock source from pin P2.4 shared by TIM0/TIM1, and pin

P2.5 shared by TIM2/TIM3. Frequency of these external clocks must be at least 4 times

less the frequency of the internal CCU PCLK clock output.

●

Two dedicated 16-bit Input Capture registers for measuring up to two input signals. Input

Capture has programmable selection of input signal edge detection

●

Two dedicated 16-bit Output Compare registers for generation up to two output signals

●

PWM output generation with 16-bit resolution of both pulse width and frequency

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