ADT7516 datasheet(39/44 Pages) AD

39 / 44 page

ADT7516/ADT7517/ADT7519

Rev. B | Page 39 of 44

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

ADDRESS POINTER REGISTER BYTE

ACK. BY

ADT7516/ADT7517/ADT7519

ACK. BY

ADT7516/ADT7517/ADT7519

ACK. BY

ADT7516/ADT7517/ADT7519

STOP BY

MASTER

FRAME 3

DATA BYTE

SDA (CONTINUED)

SCL (CONTINUED)

SCL

SDA

START BY

MASTER

R/W

Figure 61. I2C—Writing to the Address Pointer Register Followed by a Single Byte of Data to the Selected Register

SDA

START BY

MASTER

STOP BY

MASTER

NO ACK. BY

MASTER

ACK. BY

ADT7616/ADT7517/ADT7519

SCL

R/W

FRAME 1

SERIAL BUS ADDRESS BYTE

FRAME 2

SINGLE DATA BYTE FROM ADT7516/ADT7517/ADT7519

Figure 62. I2C—Reading a Single Byte of Data from a Selected Register

Writing Data to a Register

All registers are 8-bit registers, therefore only one byte of data

can be written to each register. Writing a single byte of data to

one of these read/write registers consists of the serial bus

address, the data register address written to the address pointer

one byte of data is sent in one communication operation, the

addressed register is repeatedly loaded until the last data byte

has been sent.

Reading Data from the ADT7516/ADT7517/ADT7519

Reading data from the ADT7516/ADT7517/ADT7519 is done

in a one-byte operation. Reading back the contents of a register

is shown in Figure 62. The register address had previously been

set up by a single-byte write operation to the address pointer

pointer register again to set up the relevant register address.

Thus, block reads are not possible, that is, no I2C auto-increment.

SPI Serial Interface

The SPI serial interface of the ADT7516/ADT7517/ADT7519

consists of four wires: CS , SCLK, DIN, and DOUT. The CS is

used to select the device when more than one device is connected

to the serial clock and data lines. The CS is also used to

distinguish between any two separate serial communications

(see Figure 67 for a graphical explanation). The SCLK is used to

clock data in and out of the part. The DIN line is used to write

to the registers, and the DOUT line is used to read data back

from the registers. The recommended pull-up resistor value is

between 500 Ω and 820 Ω. Strong pull-ups are needed when

serial clock speeds that are close to the maximum limit are used

or when the SPI interface lines are experiencing large capacitive

loading. Larger resistor values can be used for pull-up resistors

when the serial clock speed is reduced.

The part operates in slave mode and requires an externally

applied serial clock to the SCLK input. The serial interface is

designed to allow the part to be interfaced to systems that

provide a serial clock that is synchronized to the serial data.

There are two types of serial operations, read and write.

Command words are used to distinguish read operations from

write operations. These command words are given in Table 23.

Address auto-increment is possible in SPI mode.

Table 23. SPI Command Words

Write

Read

0x90 (1001 0000)

0x91 (1001 0001)

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