Intel CONTROLLERS 413808 - Manual (Page 694)

Intel ® 413808 and 413812—I 2 C Bus Interface Units
Intel ® 413808 and 413812 I/O Controllers in TPER Mode
Developer’s Manual October 2007
694 Order Number: 317805-001US
14.2.2 I
2
C Bus Interface Modes
The I
2
C Bus Interface Unit can be in different modes of operation to accomplish a
transfer. Table 465 summarizes the different modes.
While the I
2
C Bus Interface Unit is in idle mode (neither receiving or transmitting serial
data), the unit defaults to Slave-Receive mode. This allows the interface to monitor the
bus and receive any slave addresses that might be intended for the 4138xx.
When the I
2
C Bus Interface Unit receives an address that matches the 7-bit address
found in the I
2
C Slave Address Register (ISAR) or the General Call Address (00H), the
interface either remains in Slave-Receive mode or transitions to Slave-Transmit mode.
This is determined by the Read/Write (R/W#) bit (the least significant bit of the byte
containing the slave address). When the R/W# bit is low, the master initiating the
transaction intends to do a write and the I
2
C Bus Interface Unit remains in
Slave-Receive mode. When the R/W# is high, the initiating master wants to read data
and the slave transitions to Slave-Transmit mode. Slave operation is further defined in
Section 14.3.5, “Slave Operations” on page 705 .
When the 4138xx wants to initiate a read or write on the I
2
C bus, the I
2
C Bus Interface
Unit transitions from the default Slave-Receive mode to Master-Transmit mode. When
the 4138xx wants to write data, the interface remains in Master-Transmit mode after
the address transfer has completed. (see Section 14.2.3.1, “START Condition” on
page 696 ) for START information). When the 4138xx wants to read data, the I
2
C Bus
Interface Unit transmits the start address, then transition to Master-Receive mode.
Master operation is further defined in Section 14.3.4, “Master Operations” on page 702 .
Table 465. Modes of Operation
Mode Definition
Master — Transmit
• I 2 C Bus Interface Unit acts as a master.
• Used for a write operation.
• I 2 C Bus Interface Unit sends the data.
• I 2 C Bus Interface Unit is responsible for clocking.
• Slave device is in slave-receive mode
Master — Receive
• I 2 C Bus Interface Unit acts as a master.
• Used for a read operation.
• I 2 C Bus Interface Unit receives the data.
• I 2 C Bus Interface Unit is responsible for clocking.
• Slave device is in slave-transmit mode
Slave — Transmit
• I 2 C Bus Interface Unit acts as a slave.
• Used for a read (master) operation.
• I 2 C Bus Interface Unit sends the data.
• Master device is in master-receive mode.
Slave — Receive (default)
• I 2 C Bus Interface Unit acts as a slave.
• Used for a write (master) operation.
• I 2 C Bus Interface Unit receives the data.
• Master device is in master-transmit mode.