AD7294BCPZRL datasheet(36/48 Pages) AD

36 / 48 page

Data Sheet

AD7294

Rev. I | Page 35 of 47

SERIAL BUS ADDRESS BYTE

The first byte the user writes to the device is the slave address

byte. Similar to all I2C-compatible devices, the AD7294 has a

7-bit serial address. The 5 LSBs are user-programmable by the

3 three-state input pins, as shown in Table 34.

In Table 34, H means tie the pin to VDRIVE, L means tie the pin

to DGND, and NC refers to a pin left floating. Note that in this

final case, the stray capacitance on the pin must be less than

30 pF to allow correct detection of the floating state; therefore,

any PCB trace must be kept as short as possible.

Table 34. Slave Address Control Using Three-State Input Pins

AS2

AS1

AS0

Slave Address (A6 to A0)

0x61

0x62

0x63

0x64

0x65

0x66

0x67

0x68

0x69

0x6A

0x6B

0x6C

0x6D

0x6E

0x6F

0x70

0x71

0x72

0x73

0x74

0x75

0x76

0x77

0x78

0x79

0x7A

0x7B

INTERFACE PROTOCOL

The AD7294 uses the following I2C protocols.

Writing a Single Byte of Data to an 8-Bit Register

The alert registers (0x05, 0x06, 0x07), power-down register

(0x0A), channel sequence register (0x08), temperature offset

registers (0x26, 0x27), and the command register (0x00) are

8-bit registers; therefore, only one byte of data can be written to

each. In this operation, the master device sends a byte of data to

the slave device (see Figure 51). To write data to the register, the

command sequence is as follows:

1. The master device asserts a start condition.

2. The master sends the 7-bit slave address followed by a zero

for the direction bit, indicating a write operation.

3. The addressed slave device asserts an acknowledge on SDA.

4. The master sends a register address.

5. The slave asserts an acknowledge on SDA.

6. The master sends a data byte.

7. The slave asserts an acknowledge on SDA.

8. The master asserts a stop condition to end the transaction.

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