MMs Lect Ch-12 of 24Apr 14

8/16/2019 MMs Lect Ch-12 of 24Apr 14

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The x86 PC Assembly Language, Design, and Interfacing

By Muhammad Ali Mazidi, Janice Gillespie Mazidi and Danny Causey

© 2010, 2003, 2000, 1998 Peas!n "i#he $duca%i!n, &nc'

Peas!n Pen%ice "all ( )ppe *addle +ie, -J 0./8

Ch Twelve

INTERFACINGTO LCD, MOTOR,

ADC, AND SENSOR

8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14






12.4: INTERFACING TO ADC CHIPS & SENSORSADC devices

• The physical world is analog (continuous).

– Temperature, pressure (wind or liquid), humidity, andvelocity are examples of physical quantities.

– Digital computers use binary (discrete) values,

• physical quantity is converted to electrical

(voltage, current) signals using a device called

a transducer . (lso referred to as sensors)

• nalog!to!digital converters are widely used

devices for translating analog sensor signalsto digital num"ers so the #$ can read them.

8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14


CS, chip select ! active-low input used to activate the %&% chip. To access %&%,

this pin must "e low .

8/16/2019 MMs Lect Ch-12 of 24Apr 14


12.4: INTERFACING TO ADC CHIPS & SENSORS

ADC0848 chip pins

8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14






8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14



ADC0848 chip pins• AGND, DGND (analog ground, digital

ground) !input pins providing theground for "oth the

analog and the digital signal.

– nalog ground is connected to the ground

of the analog Vin.

– Digital ground is connected to the ground

of the VCC pin.

8/16/2019 MMs Lect Ch-12 of 24Apr 14



ADC0848 chip pins

Figure 12-14 'electing a $hannel and ead Timing for D$%&%

8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14


8/16/2019 MMs Lect Ch-12 of 24Apr 14







interfacing a temperature sensor to PC • Transducers convert physical quantities to electrical

signals. – Depending on the transducer, the output produced is in

the form of voltage, current, resistance, or capacitance.

• Temperature is converted to electrical signals using

a thermistor , a transducer

which responds to

temperature change "y

changing its resistance. – esponse is not linear,

as shown.

8/16/2019 MMs Lect Ch-12 of 24Apr 14







interfacing a temperature sensor to PC • $omplexity with writing software for such nonlinear

devices has to the linear temperature sensor. – *ncluding the +-& and +- series from /ational

'emiconductor $orp.

8/16/2019 MMs Lect Ch-12 of 24Apr 14







LM34 and LM35 temperature sensors• +34 series sensors are precision integrated!circuit

temperature sensors with output voltage linearlyproportional to the Fahrenheit temperature.

– equires no external cali"ration, as it is inherently

cali"rated, outputting 0 m1 for each degree Fahrenheit .

8/16/2019 MMs Lect Ch-12 of 24Apr 14







LM34 and LM35 temperature sensors• +35 series sensors are precision integrated!circuit

temperature sensors with output voltage linearlyproportional to Celsius (centigrade) temperature.

– equires no external cali"ration, as it is inherently

cali"rated, outputting 0 m1 for each degree centigrade.

8/16/2019 MMs Lect Ch-12 of 24Apr 14







signal conditioning/interfacing LM35/PC • ost common transducers produce

output as voltage, current, charge,capacitance 2 resistance.

– Signal conditioning is a widely used term

for the conversion of these signals to

voltage to send to an !to!D converter.• $urrent!to!voltage conversion or a signal

amplification.

• The change of resistance in a

thermistor must "e translated tovoltage to "e of use to an D$.

– s in connecting an +- to an D$%&%

8/16/2019 MMs Lect Ch-12 of 24Apr 14







signal conditioning/interfacing LM35/PC • $onnection of the temperature sensor to $34

of the D$%&%.

Figure 12-17 %4 $onnection to D$%&% and Temperature 'ensor

The +--5!4.

should overcome

fluctuations inthe power

supply.

The +--5!4.

6ener diode is

used to fix the

voltage across

the 07 #8T at4. volts.

8/16/2019 MMs Lect Ch-12 of 24Apr 14







signal conditioning/interfacing LM35/PC • $onnection of the temperature sensor to $34

of the D$%&%.

8/16/2019 MMs Lect Ch-12 of 24Apr 14






Figure 12-18 D$ %%9%:


ADC808/809• D$%%9%: has eight input channels.

– To convert % different analog inputs.• n %!"it D$.

8/16/2019 MMs Lect Ch-12 of 24Apr 14



ADC808/809 pins

• OE, output ena"le ! an active-high input signal.

– D$ converts analog input to "inary equivalent

and holds it in an internal register.

• OE is used to get the converted data out of the D$%% chip.

• SC, start conversion ! an input pin used to inform

D$%% to start the conversion process.

– The amount of time it ta7es to convert varies

depending on the CL value.

• CL ! is an input pin, connected to an external

cloc7 source.

– D$%&% uses an internal cloc7; D$%%,

external.

• EOC end of conversion an active low

8/16/2019 MMs Lect Ch-12 of 24Apr 14



ADC808/809 pins

• EOC, end of conversion ! an active-low

output pin. – /ormally high, after EOC goes low, a low!to!high pulse

is sent to the OE pin to get the data out of the D$%%.

• Vre! (<) 2 Vre! (–) ! input voltages for reference

voltage, which dictates the step si6e.

• D"#D7 ! tri!state "uffered digital data output pins.

– $onverted data is accessed only when 8= is

forced high.

• $N"#$N7 ! % channels of the Vin analog inputs.

– llows the read of % different analog signals.• /ot all at the same time, as there is only a single D–

D>.

8/16/2019 MMs Lect Ch-12 of 24Apr 14



ADC808/809 pins

• A, %, C, and ALE ! input signals to D$%%9%:.

– The channel is selected according to Ta"le 04!05.

To select achannel, provide

the channel

address to the ,

?, and $ pins

according to Ta"le04!05.

pply an L-to-H

pulse to the +=pin to latch in the

address.

8/16/2019 MMs Lect Ch-12 of 24Apr 14



how to read ADC808/809 data• D$%%9%: has a cloc7 pin, which requires an

external cloc7 source. – $onversion speed varies according to the speed of the

external cloc7 source.

– *f you use a time delay to wait "efore you read the data,

the si6e of the delay varies depending on the speedof the cloc7 connected to the cloc7 pin.

12 4

8/16/2019 MMs Lect Ch-12 of 24Apr 14







how to read ADC808/809 data - steps• 'teps to select a channel 2 read D$%%9%: data@

– 0. #rovide the channel address to pins A, %, and C.(see Ta"le 04!05)

– 4. pply an L-to-H pulse to ALE to latch in the channel

address.

– -. pply an L-to-H pulse to SC pin to start the conversionof analog input to digital data.

– &. fter % cloc7s, EOC will go low to indicate the data is

converted and ready to "e pic7ed up.

• Ase a small time delay, or monitor the =8$ pin, then readthe data out after it goes low .

– . pply an L-to-H pulse to OE pin 2 read the data.

i

8/16/2019 MMs Lect Ch-12 of 24Apr 14


The x86 PC

Assembly Language, Design, and Interfacing © 2010, 2003, 2000, 1998 Peas!n "i#he $duca%i!n, &nc'

ENDS ; TWELVE

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MMs Lect Ch-12 of 24Apr 14

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