Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
913
I
2
C Bus Interface Units—Intel
®
81341 and 81342
The I
2
C interrupts are signalled through a single pin which provides a level sensitive
interrupt to the 81341 and 81342 interrupt control unit. The I
2
C Bus Interface Unit can
cause and interrupt when a buffer is full, buffer empty, slave address detected,
arbitration lost, or bus error condition occurs. All interrupt conditions must be cleared
explicitly by software. See
Section 16.8.2, “I2C Status Register x — ISRx” on page 935
for details.
The I
2
C Data Buffer Register (IDBR) is an 8-bit data buffer that receives a byte of data
from the shift register interface of the I
2
C bus on one side and parallel data from the
81341 and 81342 internal bus on the other side. The serial shift register is not user
accessible.
The control and status registers are located in the I
2
C memory-mapped address space
which ar eat offset (+2140H to +21BFH). The registers and their function are defined in
The I
2
C Bus Interface Unit supports fast mode operation of 400 Kbits/sec. Fast mode
logic levels, formats, and capacitive loading, and protocols are exactly the same as the
100 Kbits/sec standard mode. Because the data setup and hold times differ between
the fast and standard mode, the I
2
C is designed to meet the slower, standard mode
requirements for these two specifications. Refer to the I
2
C Bus Specification for details.