ST92196A datasheet(180/268 Pages) STMICROELECTRONICS

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- FOUR-CHANNEL I2C BUS INTERFACE (I2C)

I2C BUS INTERFACE (Cont’d)

Bit 6 = ARB_LOST

Arbitration LOST detection bit

This bit indicates if an arbitration lost occurred on

the bus.

0: No arbitration lost occurred

1: An arbitration lost occurred. The bit is set when

the interface operating as a master loses arbi-

tration to another master on the bus.

If a loss of arbitration occurs during the address

byte and if the interface has been addressed by

the winning master (ACT_SLV=1), then the

ARB_LOST flag is cleared by any “data load”

operation into I2CDR.

In all other cases it is up to the user to return

the interface into the status of an inactive slave

via either a CLEAR operation, a “Return To In-

active State” operation or a STOP request.

If a loss of arbitration occurs, an interrupt is

generated: when occurring during the address

byte, the interrupt is generated at the end of the

acknowledge bit; when occurring during a data

byte, the interrupt is generated immediately.

Note: the ERROR bit has higher priority than the

ARB_LOST bit (i.e. when ERROR=1, the value of

ARB_LOST has to be ignored).

Bit 5 = READ

Read/write status bit

This flag represents the state of the read/write bit

of the address byte. It is updated either for a mas-

ter or an active slave after the end of the address

byte. It is cleared, when the interface returns to the

inactive slave status (i.e. after the normal comple-

tion of a transaction, when exiting from any error

state, ...).

0: Write operation

1: Read operation

Bit 4 = FIRST

transmission status bit

This bit indicates if the byte transmitted on the bus

is an address byte or a data byte.

0: The byte is a data byte

1: The byte is the address part of an I2C bus trans-

action.

Note: the FIRST bit is automatically cleared at the

end of the interrupt, after the address, and when

the interface returns into inactive slave state.

Bit 3 = GEN_CALL

General CALL status bit

This bit indicates if a general call has been detect-

ed on the bus.

This bit is updated only if GENC_ACK=0 (see

I2CCTR register for more details)

0: No general call detected, or GENC_ACK=1.

1: The general call address 00h has been recog-

nized by the slave.

Note: This bit is cleared by hardware when the in-

terface returns to the inactive slave status.

Bit 2 = ACK_BIT

Acknowledge BIT

This bit reflects the logic level of the acknowledge

bit detected at the end of the last byte (either ad-

dress or data) transmitted on the I2C bus. It re-

mains valid until the interface exits from the inter-

rupt state.

0: Acknowledge detected

1: No acknowledge detected

Bit 1 = ACT_SLV

Active Slave status bit

This bit indicates the slave status of the interface.

0: The interface is not working in slave mode. It

may be inactive or in master mode (see the

ACTIVE bit for more details).

1: The address assigned to the interface has been

received on the bus and has been acknowl-

edged by the interface (SEND_ACK=0).

Note: This bit is cleared when the interface returns

into inactive slave state.

Bit 0 = ACTIVE

Interface Activity status bit

This bit indicates if the interface is active or not.

0: The I2C interface is inactive

1: The Interface is active. The bit is set throughout

the interval between a start condition and the

first stop condition that follows on the I2C bus.

Note: It is reset by the CLEAR bit.

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