ADT7302ARM AD [Analog Devices], ADT7302ARM Datasheet - Page 9

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

Preliminary Technical Data
SERIAL INTERFACE
The serial interface on the ADT7302 consists of four wires: CS,
SCLK, DIN, and DOUT. The interface can be operated in 2-
wire mode with CS and DIN tied to ground, in which case the
inter-face has read-only capability, with data being read from
the data register via the DOUT line. It is advisable to utilize CS,
which improves synchronization between the ADT7302 and the
master device. The DIN line is used to write the part into
standby mode, if required. The CS line is used to select the
device when more than one device is connected to the serial
clock and data lines.
The part operates in a slave mode and requires an externally
applied serial clock to the SCLK input to access data from the
data register. The serial interface on the ADT7302 allows the
part to be interfaced to systems that provide a serial clock
synchronized to the serial data, such as the 80C51, 87C51,
68HC11, 68HC05 and PIC16Cxx microcontrollers as well as
DSP processors.
A read operation from the ADT7302 accesses data from the
temperature value register while a write operation to the part
writes data to the control register.
DOUT
SCLK
DIN
CS
t
1
1
LEADING ZEROS
2
t
2
Figure 13. Serial Interface Timing Diagram
t
3
3
t
5
DB13
POWER-
DOWN
t
6
t
Rev. PrE | Page 9 of 14
4
4
DB12
Read Operation
Figure 13 shows the timing diagram for a serial read from the
ADT7302. The CS line enables the SCLK input. Thirteen bits of
data plus a sign bit are transferred during a read operation.
Read operations occur during streams of 16 clock pulses. The
first two bits out are leading zeros and the next 14 bits contain
the temperature data. If CS remains low and 16 more SCLK
cycles are applied, the ADT7302 loops around and outputs the
two leading zeros plus the 14 bits of data that are in the temper-
ature value register. When CS returns high, the DOUT line goes
into three-state. Data is clocked out onto the DOUT line on the
falling edge of SCLK.
Write Operation
Figure 13 also shows the timing diagram for a serial write to the
ADT7302. The write operation takes place at the same time as
the read operation. Only the third bit in the data stream
provides a user-controlled function. This third bit is the power-
down bit, which, when set to a 1, puts the ADT7302 into
shutdown mode. Besides the power-down bit, all bits in the
input data stream should be zero to ensure correct operation of
the ADT7302. Data is loaded into the control register on the
16
the part is programmed to go into shutdown, it does so at this
point. If CS is brought high before this 16
control register is not loaded and the power-down status of the
part does not change. Data is clocked into the ADT7302 on the
rising edge of SCLK.
th
rising SCLK edge; the data takes effect at this time, i.e., if
15
DB1
16
t
DB0
7
t
8
th
SCLK edge, the
ADT7302