ADT7302ARM AD [Analog Devices], ADT7302ARM Datasheet - Page 10

• Manufacturer Part Number: ADT7302ARM
• Manufacturer: AD [Analog Devices]

ADT7302
MICROPROCESSOR INTERFACING
The ADT7302’ s serial interface allows for easy interface to most
microcomputers and microprocessors. Figure 14 through
Figure 17 show some typical interface circuits. The serial
interface on the ADT7302 consists of four wires: CS, DIN,
DOUT and SCLK. All interface circuits shown utilize 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 ADT7302, the DIN line can be tied
permanently low. Thus, the interface can be operated from just
three wires: SCLK, CS, and DOUT.
The serial data transfer to and from the ADT7302 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 trans-
fers. Other microcontrollers and DSP processors transfer 16 bits
of data in a serial data operation.
ADT7302 to MC68HC11 Interface
Figure 14 shows an interface between the ADT7302 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 ADT7302 in two 8-bit serial data operations. The
diagram shows the full (4-wire) interface. PC1 of the
MC68HC11 is configured as an output and is used to drive the
CS input.
ADT7302 to 8051 Interface
An interface circuit between the ADT7302 and the microcon-
troller is shown in Figure 15. 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 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.
*ADDITIONAL PINS OMITTED FOR CLARITY
ADT7302*
Figure 14. ADT7302 to MC68HC11 Interface
DOUT
SCLK
DIN
CS
SCLK
MISO
MOSI
PC1
MC68HC11*
Rev. PrE | Page 10 of 14
In the example shown, the ADT7302 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 ADT7302 is tied
low in the interface example given in Figure 15.
For applications that require the ADT7302’ s 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 “bit-banging” a port
line to generate a serial clock while using two other port lines to
shift data in and out with the fourth port line connecting to CS.
Port lines 1.0 through 1.3 (with P1.1 configured as an input)
can be used to connect to SCLK, DOUT, DIN, and CS,
respectively, to implement this scheme.
ADT7302 to PIC16C6x/7x and PIC16F873 Interface
Figure 16 shows an interface circuit between the ADT7302 and
the PIC16C6x/7x microcontroller. The PIC16C6x/7x
synchronous 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 ADT7302 in two
8-bit serial data operations. In the example shown, port line
RA1 is being used to generate the CS for the ADT7302.
The following software program shows how to program an
PIC16F873 to communicate with the ADT7302. The
PIC16F873 is configured as an SPI master with the PortA.1 pin
used as CS. Any Microchip microcontroller can use this
program by simply exchanging the include file for the device
that’s being used.
*ADDITIONAL PINS OMITTED FOR CLARITY
*ADDITIONAL PINS OMITTED FOR CLARITY
ADT7302*
Figure 16. ADT7302 to PIC16C6x/7x Interface
ADT7302*
Figure 15. ADT7302 to 8051 Interface
DOUT
DOUT
SCLK
SCLK
DIN
DIN
CS
CS
Preliminary Technical Data
P3.1
P3.0
P1.2
P1.3
SCK
SDO
SDI
RA1
PIC16C6x/7x*
8051*