Intel® PXA26x Processor Family Developer’s Manual 9-17
Inter-Integrated Circuit Bus Interfac e Un i t
master-transmitter. Figure9-14 shows a general call address transaction. The least sig nifican t b it of
the second byte, called B, defines the transaction. Table 9-7 shows the valid values and definitions
when B=0.
The I2C unit supports sending and receiving general call address transfers on the I2C bus. When
software sends a general call message from the I2C unit, it must set the ICR[GCD] bit to prevent
the I2C unit from responding as a slave. If the ICR[GCD] is not set, the I2C bus enters an
indeterminate state.
If the I2C unit acts as a slave and receives a general call address while the ICR[GCD] bit is clear, it:
Sets the ISR[GCAD] bit
Sets the ISR[SAD] bit
Interrupts the processor (if the interrupt i s enabled)
If the I2C unit receives a general call address and the ICR[GCD] bit is set, it ignores the general
call address.
Software must ensure that the I2C unit is not busy before it asserts a reset. Softwa re must also
ensure that the I2C bus is idle when the unit is enabled after reset. When directed to reset, the I2C
unit, except for ISAR, returns to the default reset condition. IS AR is not affected by a reset.
When B=1, the sequenc e is a hardware genera l call and is not suppo rted by the I2C unit. Refer to
the I2C-Bus Specification for information on hardware gen eral calls.
I2C 10-bit addresses and CBUS compatibility are not supported.
Figure 9-14. General Call Address
Table 9-7. General Call Address Second Byte Definitions
Least
Significant
Bit of Second
Byte (B)
Second
Byte
Value Definition
00x06
2-byte transaction in which the second byte tells the slave to reset and store this
value in the programmable part of its address.
00x04
2-byte transaction in which the second byte tells the slave to store this value in
the programmable part of its address. No reset.
0 0x00 Not allowed as a second byte
NOTE: Other values are not fixed and must be ignored.
Master to Slave Slave to Master
START 00000000 ACK Data
Byte ACK Data
Byte STOP
N Bytes + ACK
Least Significant Bit of Master Address
ACK
Second Byte
Second Byte 0 ACK
First Byte
Defines Transaction