I2C-COMPATIBLE 2-WIRE SERIAL BUS" />
參數(shù)資料
型號: AD5252BRU1
廠商: Analog Devices Inc
文件頁數(shù): 13/28頁
文件大?。?/td> 0K
描述: IC DIG POT DUAL 256 1K 14-TSSOP
標準包裝: 96
接片: 256
電阻(歐姆): 1k
電路數(shù): 2
溫度系數(shù): 標準值 650 ppm/°C
存儲器類型: 非易失
接口: I²C(設備位址)
電源電壓: 2.7 V ~ 5.5 V,±2.25 V ~ 2.75 V
工作溫度: -40°C ~ 85°C
安裝類型: 表面貼裝
封裝/外殼: 14-TSSOP(0.173",4.40mm 寬)
供應商設備封裝: 14-TSSOP
包裝: 管件
AD5251/AD5252
Data Sheet
Rev. D | Page 20 of 28
I2C-COMPATIBLE 2-WIRE SERIAL BUS
SDA
FRAME 1
SLAVE ADDRESS BYTE
FRAME 2
INSTRUCTION BYTE
SCL
ACK. BY
AD525x
ACK. BY
AD525x
ACK. BY
AD525x
FRAME 1
DATA BYTE
STOP BY
MASTER
03823-0-013
START BY
MASTER
0
1
0
1
AD1 AD0 R/W
X
D7
D6
D5
D4
D3
D2
D1
D0
9
1
9
1
9
Figure 33. General I2C Write Pattern
03823-0-014
SDA
FRAME 1
SLAVE ADDRESS BYTE
FRAME 2
RDAC REGISTER
SCL
ACK. BY
AD525x
NO ACK. BY
MASTER
STOP BY
MASTER
START BY
MASTER
0
1
0
1
AD1 AD0
D7
D6
D5
D4
D3
D2
D1
D0
9
1
9
R/W
Figure 34. General I2C Read Pattern
The first byte of the AD5251/AD5252 is a slave address byte
(see Figure 33 and Figure 34). It has a 7-bit slave address and an
R/W bit. The 5 MSB of the slave address is 01011, and the next
2 LSB is determined by the states of the AD1 and AD0 pins.
AD1 and AD0 allow the user to place up to four
AD5251/AD5252 devices on one bus.
AD5251/AD5252 can be controlled via an I2C-compatible serial
bus and are connected to this bus as slave devices. The 2-wire
I2C serial bus protocol (see Figure 33 and Figure 34) follows:
1. The master initiates a data transfer by establishing a start
condition, such that SDA goes from high to low while SCL
is high (see Figure 33). The following byte is the slave address
byte, which consists of the 5 MSB of a slave address defined
as 01011. The next two bits are AD1 and AD0, I2C device
address bits. Depending on the states of their AD1 and
AD0 bits, four AD5251/AD5252 devices can be addressed
on the same bus. The last LSB, the R/W bit, determines
whether data is read from or written to the slave device.
The slave whose address corresponds to the transmitted
address responds by pulling the SDA line low during the
ninth clock pulse (this is called an acknowledge bit). At
this stage, all other devices on the bus remain idle while
the selected device waits for data to be written to or read
from its serial register.
2. In the write mode (except when restoring EEMEM to the
RDAC register), there is an instruction byte that follows
the slave address byte. The MSB of the instruction byte is
labeled CMD/REG. MSB = 1 enables CMD, the command
instruction byte; MSB = 0 enables general register writing.
The third MSB in the instruction byte, labeled EE/RDAC,
is true when MSB = 0 or when the device is in general
writing mode. EE enables the EEMEM register, and REG
enables the RDAC register. The 5 LSB, A4 to A0, designates
the addresses of the EEMEM and RDAC registers (see
Figure 27 and Figure 28). When MSB = 1 or when the device
is in CMD mode, the four bits following the MSB are C3 to
C1, which correspond to 12 predefined EEMEM controls
and quick commands; there are also four factory-reserved
commands. The 3 LSB—A2, A1, and A0—are addresses,
but only 001 and 011 are used for RDAC1 and RDAC3,
respectively (see Figure 31). After acknowledging the
instruction byte, the last byte in the write mode is the data
byte. Data is transmitted over the serial bus in sequences of
nine clock pulses (eight data bits followed by an acknowledge
bit). The transitions on the SDA line must occur during the
low period of SCL and remain stable during the high period
of SCL (see Figure 33).
3. In current read mode, the RDAC0 data byte immediately
follows the acknowledgment of the slave address byte.
After an acknowledgement, RDAC1 follows, then RDAC2,
and so on. (There is a slight difference in write mode,
where the last eight data bits representing RDAC3 data are
followed by a no acknowledge bit.) Similarly, the transitions
on the SDA line must occur during the low period of SCL
and remain stable during the high period of SCL (see
Figure 34). Another reading method, random read
method, is shown in Figure 30.
4. When all data bits have been read or written, a stop
condition is established by the master. A stop condition is
defined as a low-to-high transition on the SDA line that
occurs while SCL is high. In write mode, the master pulls
the SDA line high during the 10th clock pulse to establish a
stop condition (see Figure 33). In read mode, the master
issues a no acknowledge for the ninth clock pulse, that is,
the SDA line remains high. The master brings the SDA line
low before the 10th clock pulse and then brings the SDA
line high to establish a stop condition (see Figure 34).
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