Z8 Encore!® 64K Series
Product Specification
146
13. The I2C Controller shifts the data out of using the SDA signal. After the first bit is
sent, the Transmit interrupt is asserted.
14. If more bytes remain to be sent, return to step 9.
15. Software responds by setting the STOPbit of the I2C Control register (or START bit
to initiate a new transaction). In the STOP case, software clears the TXIbit of the I2C
Control register at the same time.
16. The I2C Controller completes transmission of the data on the SDA signal.
17. The slave may either Acknowledge or Not Acknowledge the last byte. Because either
the STOP or START bit is already set, the NCKI interrupt does not occur.
18. The I2C Controller sends the STOP (or RESTART) condition to the I2C bus. The
STOP or START bit is cleared.
Address Only Transaction with a 10-bit Address
In the situation where software wants to determine if a slave with a 10-bit address is
responding without sending or receiving data, a transaction can be done which only con-
sists of an address phase. Figure 30 illustrates this “address only” transaction to determine
if a slave with 10-bit address will acknowledge. As an example, this transaction can be
used after a “write” has been done to a EEPROM to determine when the EEPROM com-
pletes its internal write operation and is once again responding to I2C transactions. If the
slave does not Acknowledge the transaction can be repeated until the slave is able to
Acknowledge.
Slave Address
1st 7 bits
Slave Address
2nd Byte
S
W = 0 A/A
A/A P
Figure 30. 10-Bit Address Only Transaction Format
The procedure for an address only transaction to a 10-bit addressed slave is as follows:
1. Software asserts the IENbit in the I2C Control register.
2. Software asserts the TXIbit of the I2C Control register to enable Transmit interrupts.
3. The I2C interrupt asserts, because the I2C Data register is empty (TDRE = 1)
4. Software responds to the TDREinterrupt by writing the first slave address byte. The
least-significant bit must be 0 for the write operation.
5. Software asserts the START bit of the I2C Control register.
6. The I2C Controller sends the START condition to the I2C slave.
PS019915-1005
I2C Controller
ZILOG [ ZILOG, INC. ]
