ST72774 datasheet(92/144 Pages) STMICROELECTRONICS

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ST72774/ST727754/ST72734

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I²C SINGLE MASTER BUS INTERFACE (Cont’d)

I2C STATUS REGISTER 1 (SR1)

Read Only

Reset Value: 0000 0000 (00h)

Bit 7 = EVF

Event flag.

This bit is set by hardware as soon as an event

occurs. It is cleared by software reading SR2

Figure 54. It is also cleared by hardware when the

interface is disabled (PE=0).

0: No event

1: One of the following events has occurred:

– BTF=1 (Byte received or transmitted)

– SB=1 (Start condition generated)

– AF=1 (No acknowledge received after byte

transmission if ACK=1)

– Address byte successfully transmitted.

Bit 6 = Reserved. Forced to 0 by hardware.

Bit 5 = TRA

Transmitter/Receiver.

When BTF is set, TRA=1 if a data byte has been

transmitted. It is cleared automatically when BTF

is cleared. It is also cleared by hardware when the

interface is disabled (PE=0).

0: Data byte received (if BTF=1)

1: Data byte transmitted

Bit 4 = Reserved. Forced to 0 by hardware.

Bit 3 = BTF

Byte transfer finished.

This bit is set by hardware as soon as a byte is

correctly received or transmitted with interrupt

generation if ITE=1. It is cleared by software

reading SR1 register followed by a read or write of

DR register. It is also cleared by hardware when

the interface is disabled (PE=0).

– Following a byte transmission, this bit is set after

reception of the acknowledge clock pulse. In

case an address byte is sent, this bit is set only

after the EV2 event (See Figure 54). BTF is

cleared by reading SR1 register followed by writ-

ing the next byte in DR register.

– Following a byte reception, this bit is set after

transmission of the acknowledge clock pulse if

ACK=1. BTF is cleared by reading SR1 register

followed by reading the byte from DR register.

The SCL line is held low while BTF=1.

0: Byte transfer not done

1: Byte transfer succeeded

Bit 2 = Reserved. Forced to 0 by hardware.

Bit 1 = M/IDL

Master/Idle.

This bit is set by hardware as soon as the interface

is in Master mode (writing START=1). It is cleared

by hardware after generating a Stop condition on

the bus. It is also cleared when the interface is

disabled (PE=0).

0: Idle mode

1: Master mode

Bit 0 = SB

Start bit generated.

This bit is set by hardware as soon as the Start

condition

generated

(following

write

START=1). An interrupt is generated if ITE=1. It is

cleared by software reading SR1 register followed

by writing the address byte in DR register. It is also

cleared by hardware when the interface is disabled

(PE=0).

0: No Start condition

1: Start condition generated

EVF

TRA

BTF

M/IDL

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