CR14 datasheet(21/46 Pages) STMICROELECTRONICS

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CR14

4 CR14 I²C protocol description

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4.7

CR14 I²C Read Operations

To send a Read command, the bus master sends a START condition, followed by a Device

Select Code and the R/W bit set to ’1’.

The CR14 that corresponds to the Device Select Code acknowledges and outputs the first data

Byte of the addressed register.

To select a specific register, a dummy Write command must first be issued, giving an address

Byte but no data Bytes, as shown in the bottom half of Figure 9. This causes the new address

to be stored in the internal address pointer, for use by the Read command that immediately

follows the dummy Write command.

In the I²C Read mode, the CR14 may read one or more data Bytes depending on the selected

data in a continuous stream. Only the last data Byte should not be followed by an ACK. The

master then terminates the transfer with a STOP condition, as shown in Figure 9.

After reading each Byte, the CR14 waits for the master to send an ACK during the 9th bit time.

If the master does not return an ACK within this time, the CR14 terminates the data transfer

and switches to stand-by mode.

Figure 9.

CR14 I²C Read Modes Sequences

CR14 READ

DEV SEL

DATA 1

DATA 2

DATA 3

AI12064

DATA N

ACK

R/W

ACK

NoACK

BUS Master

BUS Slave

ACK

DATA 4

CR14 READ

DEV SEL

ADDRESS

ACK

BUS Master

BUS Slave

R/W

ACK

DEV SEL

DATA 1

DATA N

ACK

R/W

ACK

NoACK

DATA 2

I²C CURRENT ADDRESS READ

I²C RANDOM ADDRESS READ

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