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AT42QT1060 [DATASHEET]

9505H–AT42–04/2015

4.3

Data Read/Write

4.3.1

Writing Data to the Device

The sequence of events required to write data to the device is shown next

.

1.

The host initiates the transfer by sending the START condition

2.

The host follows this by sending the slave address of the device together with the WRITE bit.

3.

The device sends an ACK.

4.

The host then sends the memory address within the device it wishes to write to.

5.

The device sends an ACK.

6.

The host transmits one or more data bytes; each is acknowledged by the device.

7.

If the host sends more than one data byte, they are written to consecutive memory addresses.

8.

The device automatically increments the target memory address after writing each data byte.

9.

After writing the last data byte, the host should send the STOP condition.

Note: the host should not try to write beyond address 255 because this is the limit of the device’s internal memory

address.

4.3.2

Reading Data From the Device

The sequence of events required to read data from the device is shown next.

1.

The host initiates the transfer by sending the START condition

2.

The host follows this by sending the slave address of the device together with the WRITE bit.

3.

The device sends an ACK.

4.

The host then sends the memory address within the device it wishes to read from.

5.

The device sends an ACK.

Table 4-1.

Description of Write Data Bits

Key

Description

S

Start condition

SLA+W

Slave address plus write bit

A

Acknowledge bit

MemAddress

Target memory address within device

Data

Data to be written

P

Stop condition

SLA+W

MemAddress

AA

S

Data

A

P

Host to Device

Device Tx to Host

SLA+W

MemAddress

AA

S

S

SLA+R

A

A

P

Host to Device

Device Tx to Host

P

A

A

Data 1

Data 2

Data n