Microchip SY89468U Bruksanvisning

Microchip Inte kategoriserad SY89468U

Läs nedan 📖 manual på svenska för Microchip SY89468U (42 sidor) i kategorin Inte kategoriserad. Denna guide var användbar för 5 personer och betygsatt med 4.5 stjärnor i genomsnitt av 2 användare

Ladda ner PDF

Sida 1/42

10-Bit A/D

Converter

Section 17. 10-Bit A/D Converter

HIGHLIGHTS

This section of the manual contains the following major topics:

17.1 Introduction ................................................................................................................. 17-2

17.2 A/D Terminology and Conversion Sequence .............................................................. 17-4

17.3 Registers..................................................................................................................... 17-6

17.4 A/D Module Configuration ......................................................................................... 17-13

17.5 Initialization ............................................................................................................... 17-16

17.6 Controlling the Sampling Process ............................................................................. 17-17

17.7 Controlling the Conversion Process.......................................................................... 17-17

17.8 A/D Results Buffer..................................................................................................... 17-23

17.9 Conversion Sequence Examples.............................................................................. 17-25

17.10 A/D Sampling Requirements..................................................................................... 17-33

17.11 Transfer Function ...................................................................................................... 17-34

17.12 A/D Accuracy/Error ................................................................................................... 17-35

17.13 Operation During Sleep and Idle Modes................................................................... 17-35

17.14 Effects of a Reset...................................................................................................... 17-36

17.15 Register Maps........................................................................................................... 17-37

17.16 Electrical Specifications............................................................................................. 17-38

17.17 Design Tips ............................................................................................................... 17-39

17.18 Related Application Notes......................................................................................... 17-40

17.19 Revision History ........................................................................................................ 17-41

PIC24F Family Reference Manual

17.1 INTRODUCTION

The PIC24F 10-bit A/D Converter has the following key features:

• Successive Approximation Register (SAR) Conversion

• Conversion Speeds of up to 500 ksps

• Up to 16 External Analog Input Channels

• Multiple Internal Reference Input Channels (select devices only)

• External Voltage Reference Input Pins

• Unipolar Differential Sample-and-Hold (S/H) Amplifier

• Automatic Channel Scan mode

• Selectable Conversion Trigger Source

• 16-Word Conversion Result Buffer

• Selectable Buffer Fill modes

• Four Options for Results Alignment

• Operation during CPU Sleep and Idle modes

The 10-bit A/D Converter module accepts a single analog signal at any one instant and converts

it to a corresponding 10-bit digital value. It accomodates up to 16 analog inputs and separate ref-

erence inputs; the actual number available on a particular device depends on the package size.

The heart of the module is a Successive Approximation Register (SAR) type of A/D Converter.

Hardware features surrounding the SAR provide flexible configuration and hardware support for

automatic operation, and minimize software overhead, especially in high-speed operation. The

three major sections surrounding the ADC are analog input selection, a memory mapped output

buffer, and timing and control functions.

An internal Sample-and-Hold (S/H) amplifier acquires a sample of an input signal, then holds that

value constant during the conversion process. A combination of input multiplexers selects the

signal to be converted from multiple analog input pins. The whole multiplexer path includes pro-

vision for differential analog input, although the number of negative input pins is limited, and the

signal difference must remain positive (i.e., unipolar). The sampled voltage is held and converted

to a digital value, which strictly speaking, represents the ratio of that input voltage to a reference

voltage. Configuration choices allow connection of an external reference or use of the device

power and ground (AVDD and AVSS). Reference and input signal pins are assigned differently

depending on the particular device.

An array of timing and control selections allow the user to create flexible scanning sequences.

Conversions can be started individually by program control, continuously free running, or triggered

by selected hardware events. A single channel may be repeatedly converted; alternate conver-

sions may be performed on two channels, or any or all of the channels may be sequentially

scanned and converted according to a user-defined bit map. The resulting conversion output is a

10-bit digital number which can be signed or unsigned, left or right justified.

Conversions are automatically stored in a dedicated 16-word buffer, allowing for multiple succes-

sive readings to be taken before software service is needed. Successive conversions are placed

into sequential buffer locations. Alternatively, the buffer can be split into two 8-word sections for

simultaneous conversion and read operations. The module sets its interrupt flag after a selectable

number of conversions, from one to sixteen, when the whole buffer can be read. After the interrupt,

the sequence restarts at the beginning of the buffer. When the interrupt flag is set according to the

earlier selection, scan selections and the Output Buffer Pointer return to their starting positions.

A simplified block diagram for the module is shown in Figure 17-1.

Section 17. 10-Bit A/D Converter

10-Bit A/D

Converter

Figure 17-1: 10-Bit A/D Converter Block Diagram

Comparator

10-Bit SAR Conversion Logic

V +REF

DAC

AN12

AN13

AN14

AN15

AN8

AN9

AN10

AN11

AN4

AN5

AN6

AN7

AN0

AN1

AN2

AN3

V -REF

Sample Control

S/H

AVSS

AVDD

ADC1BUF0:

ADC1BUFF

AD1CON1

AD1CON2

AD1CON3

AD1CHS

AD1PCFG(L)

AD1PCFGH (2)

Control Logic

Data Formatting

Input MUX Control

Conversion Control

Pin Config. Control

Internal Data Bus

V +V - RR

MUX AMUX B

VINH

VINL

VINH

VINL

VR+

VR-

VR Select

VBG(1)

VBG/2(1)

AD1CSSL

AD1CSSH(2)

Note 1: Internal analog channels are implemented in select devices only. Different device families implement different

combinations of channels. Refer to the specific device data sheet for details.

2: Implemented in select devices only.

CTMU(1)

VDDCORE(1)

AVSS(1)

AVDD(1)

PIC24F Family Reference Manual

17.2 A/D TERMINOLOGY AND CONVERSION SEQUENCE

Sample time is the time that the A/D module’s S/H amplifier is connected to the analog input pin.

The sample time may be started and ended automatically by the A/D Converter’s hardware or

under direct program control. There is a minimum sample time to ensure that the S/H amplifier

will give sufficient accuracy for the A/D conversion.

Conversion time is the time required for the A/D Converter to convert the voltage held by the

S/H amplifier. The conversion trigger ends the sampling time and begins an A/D conversion or a

repeating sequence. The conversion trigger sources can be taken from a variety of hardware

sources or can be controlled directly in software. An A/D conversion requires one A/D clock cycle

(TAD) to convert each bit of the result, plus two additional clock cycles, or a total of 12 TAD cycles

for a 10-bit conversion. When the conversion is complete, the result is loaded into one of 16 A/D

result buffers. The S/H can be reconnected to the input pin and a CPU interrupt may be gener-

ated. The sum of the sample time and the A/D conversion time provides the total A/D sequence

time. Figure 17-2 shows the basic conversion sequence and the relationship between intervals.

The conversion trigger sources can be taken from a variety of hardware sources, or can be

controlled directly by software. One of the conversion trigger options is an auto-conversion,

which uses a counter and the A/D clock to set the time between auto-conversions. The

Auto-Sample mode and auto-conversion trigger can be used together to provide continuous

automatic conversions without software intervention.

Figure 17-2: A/D Sample/Convert Sequence

Sample Time A/D Conversion Time

Total A/D Sequence Time

S/H amplifier is connected to

the analog input pin for sampling.

Input disconnected; S/H amplifier holds signal.

Conversion trigger starts A/D conversion.

Conversion complete, result is loaded

into A/D Buffer register.

Interrupt is generated (optional).

Section 17. 10-Bit A/D Converter

10-Bit A/D

Converter

R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

ADRC — — SAMC4 SAMC3 SAMC2 SAMC1 SAMC0

bit 15 bit 8

R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

ADCS7 ADCS6 ADCS5 ADCS4 ADCS3 ADCS2 ADCS1 ADCS0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15 ADRC: A/D Conversion Clock Source bit

1 = A/D internal RC clock

0 = Clock derived from system clock

bit 14-13 Unimplemented: Read as ‘0’

bit 12-8 SAMC<4:0>: Auto-Sample Time bits

11111 = 31 TAD

·····

00001 = 1 TAD

00000 = 0 TAD (not recommended)

bit 7-0 ADCS<7:0>: A/D Conversion Clock Period Select bits(1)

11111111

······ = Reserved

01000000

00111111 = 64 • Tcy

······

00000001 = 2 • TCY

00000000 = TCY

Note 1: Only valid when using the system clock as the conversion clock (ADRC = 0).

PIC24F Family Reference Manual

R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CH0NB — — CH0SB4 (1) CH0SB3 CH0SB2 CH0SB1 CH0SB0

bit 15 bit 8

R/W-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0

CH0NA — — CH0SA4 (1) CH0SA3 CH0SA2 CH0SA1 CH0SA0

bit 7 bit 0

Legend:

R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’

-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown

bit 15 CH0NB: S/H Amplifier Negative Input Select for MUX B Multiplexer Setting bit

1 = Negative input is AN1

0 = Negative input is V R-

bit 14-13 Unimplemented: Read as ‘0’

bit 12-8 CH0SB<4:0>: S/H Amplifier Positive Input Select for MUX B Multiplexer Setting bits (1)

The number of implemented analog inputs and the bit combinations assigned to them vary significantly

between device families. In general, external analog inputs, AN0 through AN15 (where implemented),

are sequentially assigned from ‘00000’ as shown below. If a sequential input is unimplemented, its

corresponding bit value is also unimplemented.

In addition, some devices implement inputs for internal band gap references, external voltage

references, and other analog modules, such as the CTMU. Refer to the specific device data sheet for

a complete listing of implemented inputs for a particular device.

Any bit combinations not explicitly listed are unimplemented. Using an unimplemented channel for a

conversion will produce unpredictable results.

01111 = Positive input is AN15

01110 = Positive input is AN14

01101 = Positive input is AN13

01100 = Positive input is AN12

01011 = Positive input is AN11

01010 = Positive input is AN10

01001 = Positive input is AN9

01000 = Positive input is AN8

00111 = Positive input is AN7

00110 = Positive input is AN6

00101 = Positive input is AN5

00100 = Positive input is AN4

00011 = Positive input is AN3

00010 = Positive input is AN2

00001 = Positive input is AN1

00000 = Positive input is AN0

bit 7 CH0NA: S/H Amplifier Negative Input Select for MUX A Multiplexer Setting bit

1 = Negative input is AN1

0 = Negative input is V R-

bit 6-5 Unimplemented: Read as ‘0’

bit 4-0 CH0SA<4:0>: S/H Amplifier Positive Input Select for MUX A Multiplexer Setting bits (1)

Implemented combinations are identical to those for CH0SB<4:0>.

Note 1: CH0SB4 and CH0SA4 are implemented in select devices only. Their implementation generally indicates

an extended range of input sources from voltage references and other analog modules.

Section 17. 10-Bit A/D Converter

10-Bit A/D

Converter

17.4 A/D MODULE CONFIGURATION

All of the registers described in the previous section must be configured for module operation to

be fully defined. An effective approach is first to describe the signals and sequences for the par-

ticular application. Typically, it is an iterative process to assign signals to port pins, to establish

timing methods and to organize a scanning scheme, as well as to integrate the whole process

with the software design.

The various configuration and control functions of the module are distributed throughout the

module’s six (or eight) control registers. Control functions can be broadly sorted into four groups:

input, timing, conversion and output. Table 17-1 shows the register location of control or status

bits by register.

Table 17-1: A/D Module Fuctions by Registers and Bits

The following steps should be followed for performing an A/D conversion.

1. Configure the A/D module:

• Select voltage reference source to match expected range on analog inputs

• Select the analog conversion clock to match desired data rate with processor clock

• Determine how sampling will occur

• Set the multiplexer input assignments

• Select the desired sample/conversion sequence

• Select the output data format

• Select the number of readings per interrupt

2. Configure A/D interrupt (if required):

• Clear AD1IF bit

• Select A/D interrupt priority

3. Turn on A/D module.

The options for each configuration step are described in the subsequent sections.

17.4.1 Selecting the Voltage Reference Source

The voltage references for A/D conversions are selected using the VCFG<2:0> control bits

(AD1CON2<15:13>). The upper voltage reference (VR+) and the lower voltage reference (VR-)

may be the internal AVDD and AVSS voltage rails or the VREF+ and VREF- input pins.

The external voltage reference pins may be shared with the AN0 and AN1 inputs on low pin count

devices. The A/D Converter can still perform conversions on these pins when they are shared

with the VREF+ and VREF- input pins.

The voltages applied to the external reference pins must meet certain specifications. Refer to

Section 17.16 “Electrical Specifications” for further details.

A/D Function Register(s) Specific Bits

Input AD1CON2 VCFG<2:0>, CSCNA, ALTS

AD1CHS CH0NB, CH0SB<4:0>, CH0NA, CH0SA<4:0>

AD1PCFG(H/L) PCFG<17:16>(1), PCFG<15:0>

AD1CSS(H/L) CSSL<17:16>(1), CSSL<15:0>

Conversion AD1CON1 ADON, ADSIDL, SSRC<2:0>, ASAM, SAMP, DONE

AD1CON2 SMPI<3:0>

Timing AD1CON3 ADRC, SAMC<4:0>, ADCS<7:0>

Output AD1CON1 FORM<1:0>

AD1CON2 BUFS, BUFM

Note 1: Implemented in select devices only.

Note: Do not write to the SSRC, ASAM, BUFS SMPI, BUFM and ALTS bits, or the

AD1CON3 and AD1CSSL registers, while ADON = 1; otherwise, indeterminate

conversion data may result.

Produktspecifikationer

Varumärke:	Microchip
Kategori:	Inte kategoriserad
Modell:	SY89468U

Behöver du hjälp?

Om du behöver hjälp med Microchip SY89468U ställ en fråga nedan och andra användare kommer att svara dig

Ditt namn*

Din e-post*

Skriv din fråga här

Inte kategoriserad Microchip Manualer

Microchip ATA6574 Bruksanvisning

12 Mars 2025

Microchip MCP4902 Bruksanvisning

12 Mars 2025

Microchip PIC18F27J53 Bruksanvisning

6 Mars 2025

Microchip AR1021 Bruksanvisning

5 Mars 2025

Microchip PIC32MX130F128H Bruksanvisning

4 Mars 2025

Microchip ATSAMA5D43 Bruksanvisning

4 Mars 2025

Microchip ATSAMC20E18A Bruksanvisning

2 Mars 2025

Microchip TC620 Bruksanvisning

2 Mars 2025

Microchip MIC5219 Bruksanvisning

2 Mars 2025

Microchip MIC3223 Bruksanvisning

2 Mars 2025

Inte kategoriserad Manualer

Nyaste Inte kategoriserad Manualer

Planet PWR-240-48 Bruksanvisning

9 April 2025

CaterChef 445001 Bruksanvisning

9 April 2025

Daikin EKWCTRDI1V3 Bruksanvisning

9 April 2025

Simplified MFG SP18CAT120 Bruksanvisning

9 April 2025

AudioQuest Pegasus Bruksanvisning

9 April 2025

Reolink P330 Bruksanvisning

9 April 2025

Reolink NVS16-8MB8 Bruksanvisning

9 April 2025

Drive Medical RTL12045 Bruksanvisning

9 April 2025

Kern MBC-A05 Bruksanvisning

9 April 2025

Daikin EKEXVA250 Bruksanvisning

9 April 2025