Datasheet ADT7301 (Analog Devices) - 11

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ADT7301 CS t1 t t 2 7 SCLK 1 2 3 4 15 16 t3 t8 t4 DOUT LEADING ZEROS DB13 DB12 DB0 DB1 DB0 t6 t5 POWER- DIN DOWN
02884-0-007 Figure 14. Serial Interface Timing Diagram
SERIAL INTERFACE Read Operation
The serial interface on the ADT7301 consists of four wires: Figure 14 shows the timing diagram for a serial read from the CS, SCLK, DIN, and DOUT. The interface can be operated in ADT7301. The CS line enables the SCLK input. Thirteen bits of 3-wire mode with DIN tied to ground, in which case the inter- data plus a sign bit are transferred during a read operation. face has read-only capability, with data being read from the data Read operations occur during streams of 16 clock pulses. The register via the DOUT line. It is advisable to always use CS to first 2 bits out are leading zeros and the next 14 bits contain the create a communications window, as shown in Figure 14; this temperature data. If CS remains low and 16 more SCLK cycles improves synchronization between the ADT7301 and the master are applied, the ADT7301 loops around and outputs the two device. The DIN line is used to write the part into standby mode, leading zeros plus the 14 bits of data that are in the temp- if required. The CS line is used to select the device when more erature value register. When CS returns high, the DOUT line than one device is connected to the serial clock and data lines. goes into three-state. Data is clocked out onto the DOUT line The part operates in a slave mode and requires an externally on the falling edge of SCLK. applied serial clock to the SCLK input to access data from the
Write Operation
data register. The serial interface on the ADT7301 al ows the part to be interfaced to systems that provide a serial clock Figure 14 also shows the timing diagram for a serial write to the synchronized to the serial data, such as the 80C51, 87C51, ADT7301. The write operation takes place at the same time as 68HC11, 68HC05, and PIC16Cxx microcontrollers as well as the read operation. Only the third bit in the data stream provides DSP processors. a user-controlled function. This third bit is the power-down bit, which, when set to 1, puts the ADT7301 into shutdown mode. A read operation from the ADT7301 accesses data from the In addition to the power-down bit, all bits in the input data temperature value register, while a write operation to the part stream should be 0 to ensure correct operation of the ADT7301. writes data to the control register. Data is loaded into the control register on the 16th rising SCLK edge; the data takes effect at this time. Therefore, if the part is programmed to go into shutdown, it does so at this point. If CS is brought high before this 16th SCLK edge, the control register is not loaded and the power-down status of the part does not change. Data is clocked into the ADT7301 on the rising edge of SCLK. Rev. B | Page 11 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 ADT7301-to-MC68HC11 Interface ADT7301-to-8051 Interface ADT7301-to-PIC16C6x/7x Interface ADT7301-to-ADSP-21xx Interface Mounting the ADT7301 Supply Decoupling Outline Dimensions Ordering Guide