17

3.2

Data Transfer Format

Figure 3-4 shows an example of data transfer in write mode.

Figure 3-4. Example of Data Transfer in Write Mode

D6

SDA

D5 D4 D3 D2 D1 D0

Slave address

D7 D6 D5 D4 D3 D2 D1 D0

Subaddress

D7 D6 D5 D4 D3 D2 D1 D0

Data

SCL

W ACK

ACK

ACK

Remark W: Write mode, ACK: Acknowledge bit

Data is composed of 8 bits. One acknowledge bit always follows these 8 bits of data. Data must be transferred

starting from the MSB.

The 1 byte immediately following the start condition specifies a slave address (chip address). This slave address

is composed of 7 bits.

Table 3-1 shows the slave address of the

µPC1857A. This slave address is registered by Philips.

Table 3-1. Slave Address of

µPC1857A

Slave Address

Bias Voltage of ADS (Pin 22)

D6

D5

D4

D3

D2

D1

Note

D0

5 V

1

000

1

1

0

GND

1

000

1

0

0

Note The user can set bit D1 freely.

0: Bias voltage of ADS (pin 22) is 0 V.

1: Bias voltage of ADS (pin 22) is 5 V.

The 1 bit following the slave address is a read/write bit which specifies the direction of the data to be subsequently

transferred. Write “0” to this read/write bit because the

µPC1857A is write mode only.

The byte following the slave address is the subaddress byte of the

µPC1857A.

The

data to be set to a subaddress follows this subaddress byte.