IDT I2C Bus Interface
I2C Register Description
79RC32438 User Reference Manual
15 - 2
November 4, 2002
Notes
internal I
2
C bus prescalar clock (I2CPCLK) that is used as a time base by the master and slave inter-
faces.
2
The internally generated I
2
C bus prescalar clock is equal to the IPBus clock input divided by the
clock prescalar divisor (DIV) field in the I
2
C bus clock prescalar (I2CCP) register.
2
The master and slave interfaces may be independently enabled and disabled at any point in time,
2
allowing the interface to operate as an I
2
C bus master, an I
2
C bus slave, or concurrently as master and
slave.
2
When configured to operate concurrently as a master and slave, it is possible for the master inter-
face to initiate transactions to the slave interface
2
(that is,
2
it is possible to perform loop-back operations).
2
A central part of the I
2
C bus interface common logic is the I
2
C bus data input (I2CDI) and I
2
C bus data
output (I2CDO) registers.
2
The I2CDI register is used by both the master and slave interfaces to receive
data from the I
2
C bus. During the data phase of any I
2
C bus operation, data present on the SDA pin is
shifted into this register. Thus, at the end of each I
2
C bus data transfer, this register contains the data byte
present on the I
2
C bus. Data to be driven onto the I
2
C bus is written to I2CDO register by the CPU. During
the data phase of an I
2
C bus transmit operation, the contents of this register are shifted out a bit at a time
on the SDA pin.
2
I
2
C Register Description
I
2
C Bus Control Register
Figure 15.2 I
2
C Bus Control Register (I2CC)
Register Offset
Register Name
Register Function
Size
0x7_0000
I2CC
I
2
C bus control
32-bit
0x7_0004
I2CDI
I
2
C bus data input
32-bit
0x7_0008
I2CDO
I
2
C bus data output
32-bit
0x7_000C
I2CCP
I
2
C bus clock prescalar
32-bit
0x7_0010
I2CMCMD
I
2
C bus master command
32-bit
0x7_0014
I2CMS
I
2
C bus master status
32-bit
0x7_0018
I2CMSM
I
2
C bus master status mask
32-bit
0x7_001C
I2CSS
I
2
C bus slave status
32-bit
0x7_0020
I2CSSM
I
2
C bus slave status mask
32-bit
0x7_0024
I2CSADDR
I
2
C bus slave address
32-bit
0x7_0028
I2CSACK
I
2
C bus slave acknowledge
32-bit
0x7_002C through 0x7_7FFF Reserved
Table 15.1 I2C Register Map
I2CC
0
31
MEN
0
29
1
SEN
1
IOM
1