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ADT7516/ADT7517/ADT7519
Any number of bytes of data can be transferred over the serial
bus in one operation, but it is not possible to mix read and write
in one operation because the type of operation is determined at
the beginning and cannot subsequently be changed without
starting a new operation.
Rev. A | Page 39 of 44
The I
2
C address set up by the ADD pin is not latched by the
device until after this address has been sent twice. On the eighth
SCL cycle of the second valid communication, the serial bus
address is latched in. This is the SCL cycle directly after the
device has seen its own I
2
C serial bus address. Any subsequent
changes on this pin will have no effect on the I
2
C serial bus
address.
Writing to the ADT7516/ADT7517/ADT7519
Depending on the register being written to, there are two
different writes for the ADT7516/ADT7517/ADT7519. It is not
possible to do a block write to this part, i.e., no I
2
C auto-
increment.
Writing to the Address Pointer Register for a
Subsequent Read
To read data from a particular register, the address pointer
register must contain the address of that register. If it does not,
the correct address must be written to the address pointer
register by performing a single-byte write operation, as shown
in Figure 60. The write operation consists of the serial bus
address followed by the address pointer byte. No data is written
to any of the data registers. A read operation is then performed
to read the register.
Writing Data to a Register
All registers are 8-bit registers, so 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 register,
followed by the data byte written to the selected data register.
This is illustrated in Figure 61. To write to a different register,
another start or repeated start is required. If more than one byte
of data is sent in one communication operation, the addressed
1
register will be 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 1-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
register. To read from another register, write to the address
pointer register again to set up the relevant register address.
Thus, block reads are not possible, i.e., no I
2
C 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 con-
nected 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 D
IN
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 and 820 .
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. Com-
mand words are used to distinguish read operations from write
operations. These command words are given in Table 67.
Address auto-increment is possible in SPI mode.
Table 67. SPI Command Words
Write
90h (1001 0000)
Read
91h (1001 0001)
0
1
R/W
SCL
SDA
FRAME 1
SERIAL BUS ADDRESS BYTE
Figure 60. I
2
C—Writing to the Address Pointer Register to Select a Register for a Subsequent Read Operation
FRAME 2
ADDRESS POINTER REGISTER BYTE
ACK. BY
ADT7516/ADT7517/ADT7519
ACK. BY
ADT7516/ADT7517/ADT7519
STOP BY
MASTER
START BY
MASTER
0
0
1
A2
A1
A
P7
P6
P5
P4
P3
P2
P1
P0
9
1
9
0