ST72F63 STMICROELECTRONICS [STMicroelectronics], ST72F63 Datasheet - Page 77

• Manufacturer Part Number: ST72F63
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

I²C BUS INTERFACE (Cont’d)
11.5.4 Functional Description
Refer to the CR, SR1 and SR2 registers in
11.5.7. for the bit definitions.
By default the I²C interface operates in Slave
mode (M/SL bit is cleared) except when it initiates
a transmit or receive sequence.
11.5.4.1 Slave Mode
As soon as a start condition is detected, the
address is received from the SDA line and sent to
the shift register; then it is compared with the
address of the interface or the General Call
address (if selected by software).
Address not matched: the interface ignores it
and waits for another Start condition.
Address matched: the interface generates in se-
quence:
– An Acknowledge pulse is generated if the ACK
– EVF and ADSL bits are set with an interrupt if the
Then the interface waits for a read of the SR1 reg-
ister, holding the SCL line low (see
Transfer sequencing EV1).
Next, software must read the DR register to deter-
mine from the least significant bit if the slave must
enter Receiver or Transmitter mode.
Slave Receiver
Following the address reception and after SR1
register has been read, the slave receives bytes
from the SDA line into the DR register via the inter-
nal shift register. After each byte the interface gen-
erates in sequence:
– An Acknowledge pulse is generated if the ACK
– EVF and BTF bits are set with an interrupt if the
Then the interface waits for a read of the SR1 reg-
ister followed by a read of the DR register, holding
the SCL line low (see
quencing EV2).
Slave Transmitter
Following the address reception and after the SR1
register has been read, the slave sends bytes from
the DR register to the SDA line via the internal shift
register.
bit is set.
ITE bit is set.
bit is set
ITE bit is set.
Figure 41
Transfer se-
Figure 41
Section
The slave waits for a read of the SR1 register fol-
lowed by a write in the DR register, holding the
SCL line low (see
EV3).
When the acknowledge pulse is received:
– The EVF and BTF bits are set by hardware with
Closing Slave Communication
After the last data byte is transferred a Stop Con-
dition is generated by the master. The interface
detects this condition and sets:
– EVF and STOPF bits with an interrupt if the ITE
Then the interface waits for a read of the SR2 reg-
ister (see
Error Cases
– BERR: Detection of a Stop or a Start condition
– AF: Detection of a non-acknowledge bit. In this
Note: In both cases, the SCL line is not held low;
however, the SDA line can remain low due to pos-
sible “0” bits transmitted last. It is then necessary
to release both lines by software.
How to Release the SDA / SCL lines
Set and subsequently clear the STOP bit while
BTF is set. The SDA/SCL lines are released after
the transfer of the current byte.
an interrupt if the ITE bit is set.
bit is set.
during a byte transfer. In this case, the EVF and
BERR bits are set with an interrupt if the ITE bit
is set.
If it is a Stop condition, then the interface dis-
cards the data, released the lines and waits for
another Start condition.
If it is a Start condition, then the interface dis-
cards the data and waits for the next slave ad-
dress on the bus.
case, the EVF and AF bits are set with an inter-
rupt if the ITE bit is set.
Figure 41
Figure 41
Transfer sequencing EV4).
Transfer sequencing
ST7263B
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