EVAL-ADT7301EBZ Datasheet ADT7301ARMZ, ADT7301ARTZ-REEL7, EVAL-ADT7301EBZ | P13-P15

ADT7301

Rev. B | Page 12 of 16

APPLICATIONS INFORMATION

MICROPROCESSOR INTERFACING

The ADT7301 serial interface allows easy interface to most

microcomputers and microprocessors. Figure 15 to Figure 18

show some typical interface circuits. The serial interface on the

ADT7301 consists of four wires:

, DIN, DOUT, and SCLK.

All interface circuits shown use all four interface lines. However,

it is possible to operate the interface with three wires. If the

application does not require the power-down facility offered

by the ADT7301, the DIN line can be tied low permanently.

Thus, the interface can be operated from just three wires: SCLK,

, and DOUT.

The serial data transfer to and from the ADT7301 requires a

16-bit read operation. Many 8-bit microcontrollers have 8-bit

serial ports, and this 16-bit data transfer is handled as two 8-bit

transfers. Other microcontrollers and DSP processors transfer

16 bits of data in a serial data operation.

ADT7301-to-MC68HC11 Interface

Figure 15 shows an interface circuit between the ADT7301 and

the MC68HC11 microcontroller. The MC68HC11 is configured

in master mode with its CPOL and CPHA bits set to a Logic 1.

When the MC68HC11 is configured like this, its SCLK line idles

high between data transfers. Data is transferred to and from the

ADT7301 in two 8-bit serial data operations. Figure 15

shows

the full (4-wire) interface. PC1 of the MC68HC11 is configured

as an output and is used to drive the

input.

ADT7301*

SCLK

DOUT

DIN

MC68HC11*

SCLK

MISO

MOSI

PC1

02884-0-008

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 15. ADT7301-to-MC68HC11 Interface

ADT7301-to-8051 Interface

Figure 16 shows an interface circuit between the ADT7301 and

the microcontroller. The 8051 is configured in its Mode 0 serial

interface mode. The serial clock line of the 8051 (on P3.1) idles

high between data transfers. Data is transferred to and from the

ADT7301 in two 8-bit serial data operations. The ADT7301

outputs the MSB of its data stream as the first valid bit while the

8051 expects the LSB first. Thus, the data read into the serial

buffer needs to be rearranged before the correct data-word from

the ADT7301 is available in the accumulator.

In the example shown in Figure 16, the ADT7301 is connected

to the serial port of the 8051. Because the serial interface of the

8051 contains only one data line, the DIN line of the ADT7301

is tied low in Figure 16.

For applications that require the ADT7301 power-down feature,

the serial interface should be implemented using data port lines

on the 8051. This allows a full-duplex serial interface to be

implemented. The method involves generating a serial clock on

one port line while using two other port lines to shift data

in and out with the fourth port line connecting to

. Port

lines 1.0 to 1.3 (with P1.1 configured as an input) can be used

to connect to SCLK, DOUT, DIN, and

, respectively, to

implement this scheme.

ADT7301*

02884-0-009

SCLK

DOUT

DIN

8051*

P3.1

P3.0

P1.2

P1.3

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 16. ADT7301-to-8051 Interface

ADT7301-to-PIC16C6x/7x Interface

Figure 17 shows an interface circuit between the ADT7301 and

the PIC16C6x/7x microcontroller. The PIC16C6x/7x synchro-

nous serial port (SSP) is configured as an SPI master with the

clock polarity bit set to a Logic 1. In this mode, the serial clock

line of the PIC16C6x/7x idles high between data transfers. Data

is transferred to and from the ADT7301 in two 8-bit serial data

operations. In the example shown in Figure 17

, port line RA1 is

being used to generate the

for the ADT7301.

ADT7301*

SCLK

DOUT

DIN

PIC16C6x/7x*

SCK

SDO

SDI

RA1

02884-0-010

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 17. ADT7301-to-PIC16C6x/7x Interface

ADT7301

Rev. B | Page 13 of 16

The following software program shows how to program a

PIC16F873 to communicate with the ADT7301. The

PIC16F873 is configured as an SPI master with the Port A.1 pin

used as

. Any microchip microcontroller can use this

program by simply exchanging the include file for the device

that is being used.

#include <16F873.h>

#device adc = 8

#use delay(clock = 4000000)

#fuses NOWDT,XT, PUT, NOPROTECT, BROWNOUT, LVP

#BIT CKP = 0x14.4

#define CS PIN_A1

void main(){

int MSByte,LSByte;

long int ADC_Temp_Code;

float TempVal,ADC_Temp_Code_dec;

setup_spi(spi_master); //Pic is set up as master device.

CKP = 1; //Idle state of clock is high.

do{

delay_ms(10); //Allow time for conversions.

Output_low(CS); //Pull CS low.

delay_us(10); //CS to SCLK set-up time.

MSByte = SPI_Read(0); //The first byte is clocked in.

LSByte = SPI_Read(0); //The second byte is clocked in.

delay_us(10); //SCLK to CS set-up time.

Output_High(CS); //Bring CS high.

ADC_Temp_Code = make16(MSByte,LSByte); //16 bit ADC code is stored ADC_Temp_Code.

ADC_Temp_Code_dec = (float)ADC_Temp_Code; //Convert to float for division.

if ((0x2000 & ADC_Temp_Code) == 0x2000) //Check sign bit for negative value.

{

TempVal = (ADC_Temp_Code_de

c - 16384)/32; //Conversion formula if negative temperature.

}

else

{

TempVal = (ADC_Temp_Code_dec/32); //Conversion formula if positive temperature.

}

}while(True);

//Temperature value stored in TempVal.

}

ADT7301

Rev. B | Page 14 of 16

ADT7301-to-ADSP-21xx Interface

Figure 18 shows an interface between the ADT7301 and the

ADSP-21xx DSP processor. To ensure correct operation of the

interface, the SPORT control register should be set up as follows:

TFSW = RFSW = 1, alternate framing

INVRFS = INVTFS = 1, active low framing signal

DTYPE = 00, right justify data

SLEN = 1111, 16-bit data-words

ISCLK = 1, internal serial clock

TFSR = RFS = 1, frame every word

IRFS = 0, RFS configured as input

ITFS = 1, TFS configured as output

The interface requires an inverter between the SCLK line of the

ADSP-21xx and the SCLK input of the ADT7301. On the

ADSP-21xx interface, the TFS and RFS of the SPORT are tied

together; TFS is set as an output, and RFS is set as an input. The

DSP operates in alternate framing mode and the SPORT control

ADT7301*

SCLK

DOUT

DIN

ADSP-21xx*

SCK

RFS

02884-0-011

*ADDITIONAL PINS OMITTED FOR CLARITY

TFS

Figure 18. ADT7301-to-ADSP-21xx Interface

MOUNTING THE ADT7301

The ADT7301 can be used for surface or air temperature

sensing applications. If the device is cemented to a surface with

a thermally conductive adhesive, the die temperature will be

within about 0.1°C of the surface temperature because of the

ADT7301’s low power consumption. Care should be taken to

insulate the back and leads of the device if the ambient air

temperature is different from the surface temperature being

measured.

The ground pin provides the best thermal path to the die;

therefore, the temperature of the die is close to that of the

printed circuit ground track. Care should be taken to ensure

that this is in good thermal contact with the measured surface.

As in any IC, the ADT7301 and its associated wiring and

circuits must be kept free from moisture to prevent leakage and

corrosion, particularly in cold conditions where condensation is

more likely to occur. Water-resistant varnishes and conformal

coatings can be used for protection. The small size of the

ADT7301 allows it to be mounted inside sealed metal probes,

which provide a safe environment for the device.

SUPPLY DECOUPLING

The ADT7301 should be decoupled with a 0.1 µF ceramic

capacitor between V

and GND. This is particularly important

if the ADT7301 mount is remote from the power supply.

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P17

EVAL-ADT7301EBZ

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Temperature Sensor Development Tools EVAL BRD ADT7301

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