UPSD3422 datasheet(123/293 Pages) STMICROELECTRONICS

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uPSD34xx

I2C interface

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Table 56.

S1STA: I2C interface status register (SFR DDh, reset value 00h)

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

STOP

INTR

TX_MODE

BBUSY

BLOST

ACK_RESP

SLV

Bit

Symbol

R/W

Function

7GC

General Call flag

GC = 1 if the General Call address of 00h was received when

SIOE is in Slave mode, and GC is cleared by a START or

STOP condition on the bus. If the SIOE is in Master mode

when GC = 1, the Bus Lost condition exists, and BLOST = 1.

6STOP

STOP flag

STOP = 1 while SIOE detects a STOP condition on the bus

when in Master or Slave mode.

5INTR

R,W

Interrupt flag

INTR is set to 1 by any of the five I2C interrupt conditions listed

above. INTR must be cleared by firmware.

4TX_MODE

Transmission Mode flag

TX_MODE = 1 whenever the SIOE is in Master-Transmitter or

Slave-Transmitter mode. TX_MODE = 0 when SIOE is in any

receiver mode.

3BBUSY

Bus Busy flag

BBUSY = 1 when the I2C bus is in use. BBUSY is set by the

SIOE when a START condition exists on the bus and BBUSY

is cleared by a STOP condition.

2BLOST

Bus Lost flag

BLOST is set when the SIOE is in Master mode and it looses

the arbitration process to another Master device on the bus.

1ACK_RESP

Not Acknowledge Response flag

While SIOE is in Transmitter mode:

– After SIOE sends a byte, ACK_RESP = 1 whenever the

external I2C device receives the byte, but that device does

NOT assert an ackowledge signal (external device asserted

a high on SDA during the acknowledge bit-time).

– After SIOE sends a byte, ACK_RESP = 0 whenever the

external I2C device receives the byte, and that device DOES

assert an ackowledge signal (external device drove a low on

SDA during the acknowledge bit-time)

Note: If SIOE is in Master-Transmitter mode, and ACK_RESP

= 1 due to a Slave-Transmitter not sending an Acknowledge, a

STOP condition will not automatically be generated by the

SIOE. The STOP condition must be generated with

S1CON.STO = 1.

0SLV

Slave Mode flag

SLV = 1 when the SIOE is in Slave mode. SLV = 0 when the

SIOE is in Master mode (default).

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