AD7879 Просмотр технического описания (PDF) - Analog Devices
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AD7879 Datasheet PDF : 40 Pages
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Data Sheet
AD7879/AD7889
16-BIT COMMAND WORD
ENABLE WORD R/W
STARTING REGISTER ADDRESS
DIN
CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW CW
15 14 13 12 11 10 9
87
6
5
4
3
2
1
0
X
X
X XXX
XX X
SCL
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
31 32 33 34
47 48 49
CS
DOUT
XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX XXX D15 D14
D1 D0 D15 D14
D1 D0 D15
READBACK DATA FOR
STARTING REGISTER
ADDRESS
READBACK DATA FOR
NEXT REGISTER ADDRESS
NOTES
1. MULTIPLE SEQUENTIAL REGISTERS CAN BE READ BACK CONTINUOUSLY.
2. THE 16-BIT COMMAND WORD MUST BE WRITTEN ON DIN: 5 BITS FOR ENABLE WORD, 1 BIT FOR R/W, AND 10 BITS FOR REGISTER ADDRESS.
3. THE ADDRESS AUTOMATICALLY INCREMENTS WITH EACH 16-BIT DATA-WORD BEING READ BACK ON THE DOUT PIN.
4. CS IS HELD LOW UNTIL ALL REGISTER BITS HAVE BEEN READ BACK.
5. X DENOTES DON’T CARE.
6. XXX DENOTES HIGH IMPEDANCE THREE-STATE OUTPUT.
7. 16-BIT COMMAND WORD SETTINGS FOR SEQUENTIAL READBACK OPERATION:
CW[15:11] = 11100 (ENABLE WORD)
CW[10] = 1 (R/W)
CW[9:0] = [AD9, AD8, AD7, AD6, AD5, AD4, AD3, AD2, AD1, AD0] (STARTING MSB JUSTIFIED REGISTER ADDRESS)
Figure 42. Sequential Register Readback, SPI Timing
I2C-COMPATIBLE INTERFACE
The AD7879-1/AD7889-1 support the industry standard 2-wire
I2C serial interface protocol. The two wires associated with the
I2C timing are the SCL and SDA inputs. SDA is an input output
pin that allows both register write and register readback operations.
The AD7879-1/AD7889-1 are always a slave device on the I2C
serial interface bus.
The devices have a 7-bit device address, Address 0101 1XX. The
lower two bits are set by tying the ADD0 and ADD1 pins high or
low. The AD7879-1/AD7889-1 respond when the master device
sends the device address over the bus. The AD7879-1/AD7889-1
cannot initiate data transfers on the bus.
Table 25. I2C Device Addresses for the AD7879-1/AD7889-1
ADD1
ADD0
I2C Address
0
0
0101 100
0
1
0101 101
1
0
0101 110
1
1
0101 111
Data Transfer
Data is transferred over the I2C serial interface in 8-bit bytes.
The master initiates a data transfer by establishing a start condition,
defined as a high-to-low transition on the serial data line, SDA,
while the serial clock line, SCL, remains high. This indicates
that an address/data stream follows.
All slave peripherals connected to the serial bus respond to the
start condition and shift in the next eight bits, consisting of a
7-bit address (MSB first) plus a R/W bit that determines the
direction of the data transfer. The peripheral whose address
corresponds to the transmitted address responds by pulling the
data line low during the ninth clock pulse. This is known as the
acknowledge bit. All other devices on the bus then remain idle
while the selected device waits for data to be read from or written
to it. If the R/W bit is a 0, the master writes to the slave device.
If the R/W bit is a 1, the master reads from the slave device.
Data is sent over the serial bus in a sequence of nine clock
pulses (eight bits of data followed by an acknowledge bit from
the slave device). Transitions on the data line must occur during
the low period of the clock signal and remain stable during the
high period because a low-to-high transition when the clock
is high can be interpreted as a stop signal. The number of data
bytes transmitted over the serial bus in a single read or write
operation is limited only by what the master and slave devices
can handle.
When all data bytes are read or written, a stop condition is
established. A stop condition is defined by a low-to-high
transition on SDA while SCL remains high. If the AD7879-1/
AD7889-1 encounter a stop condition, they return to the idle
condition.
Rev. D | Page 35 of 40
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