Datasheet ADT7302 (Analog Devices) - 12

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ADT7302 APPLICATIONS INFORMATION MICROPROCESSOR INTERFACING
In the example, the ADT7302 is connected to the serial port of The ADT7302’s serial interface allows easy interface to most the 8051. Because the serial interface of the 8051 contains only microcomputers and microprocessors. Figure 15 through one data line, the DIN line of the ADT7302 is tied low in Figure 18 show some typical interface circuits. The serial Figure 16. interface on the ADT7302 consists of four wires: CS, DIN, For applications that require the ADT7302 power-down feature, DOUT, and SCLK. All interface circuits shown use all four the serial interface should be implemented using data port lines interface lines. However, it is possible to operate the interface on the 8051. This allows a full-duplex serial interface to be with three wires. If the application does not require the power- implemented. The method involves “bit-banging” a port line to down facility offered by the ADT7302, the DIN line can be tied generate a serial clock while using two other port lines to shift low permanently. Thus, the interface can be operated from just data in and out with the fourth port line connecting to CS. Port three wires: SCLK, CS, and DOUT. lines 1.0 through 1.3 (with P1.1 configured as an input) can be The serial data transfer to and from the ADT7302 requires a used to connect to SCLK, DOUT, DIN, and CS, respectively, to 16-bit read operation. Many 8-bit microcontrol ers have 8-bit implement this scheme. serial ports, and this 16-bit data transfer is handled as two 8-bit transfers. Other microcontrollers and DSP processors transfer
ADT7302* 8051* SCLK P1.1
16 bits of data in a serial data operation.
DOUT P1.0 ADT7302 to MC68HC11 Interface DIN P1.2
Figure 15 shows an interface between the ADT7302 and the
CS P1.3
MC68HC11 microcontrol er. The MC68HC11 is configured in -016 master mode with its CPOL and CPHA bits set to a Logic 1.
*ADDITIONAL PINS OMITTED FOR CLARITY
04662 When the MC68HC11 is configured like this, its SCLK line Figure 16. ADT7302 to 8051 Interface idles high between data transfers. Data is transferred to and from the ADT7302 in two 8-bit serial data operations. Figure 15
ADT7302 to PIC16C6x/7x and PIC16F873 Interface
shows the full (4-wire) interface. PC1 of the MC68HC11 is Figure 17 shows an interface circuit between the ADT7302 and configured as an output and is used to drive the CS input. the PIC16C6x/7x microcontrol er. The PIC16C6x/7x synchronous serial port (SSP) is configured as an SPI master
ADT7302* MC68HC11*
with the clock polarity bit set to a Logic 1. In this mode, the
SCLK SCLK
serial clock line of the PIC16C6x/7x idles high between data
DOUT MISO
transfers. Data is transferred to and from the ADT7302 in two
DIN MOSI
8-bit serial data operations. In the example shown, port line
CS PC1
RA1 is being used to generate the CS for the ADT7302. -015
*ADDITIONAL PINS OMITTED FOR CLARITY
04662
ADT7302* PIC16C6x/7x*
Figure 15. ADT7302 to MC68HC11 Interface
SCLK SCLK DOUT SDO ADT7302 to 8051 Interface DIN SDI
Figure 16 shows an interface circuit between the ADT7302 and
CS RA1
the microcontroller. The 8051 is configured in its Mode 0 serial -017 interface mode. The serial clock line of the 8051 (on P3.1) idles
*ADDITIONAL PINS OMITTED FOR CLARITY
04662 high between data transfers. Data is transferred to and from the Figure 17. ADT7302 to PIC16C6x/7x Interface ADT7302 in two 8-bit serial data operations. The ADT7302 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 ADT7302 is available in the accumulator. Rev. B | Page 12 of 16 Document Outline Features Applications Functional Block Diagram General Description Product Highlights Revision History Specifications Timing Characteristics Absolute Maximum Ratings ESD Caution Pin Configurations and Function Descriptions Typical Performance Characteristics Theory of Operation Converter Details Temperature Value Register Temperature Conversion Equations Serial Interface Read Operation Write Operation Applications Information Microprocessor Interfacing ADT7302 to MC68HC11 Interface ADT7302 to 8051 Interface ADT7302 to PIC16C6x/7x and PIC16F873 Interface ADT7302 to ADSP-21xx Interface Mounting the ADT7302 Supply Decoupling Outline Dimensions Ordering Guide