Datasheet

4−33
4.46 Serial-Bus Index Register
The serial-bus index register is for programmable serial-bus byte reads and writes. This register represents the byte
address when generating cycles on the serial-bus interface. To write a byte, the serial-bus data register must be
programmed with the data, this register must be programmed with the byte address, and the serial-bus slave address
register must be programmed with both the 7-bit slave address and the read/write indicator bit.
On byte reads, the word address is programmed into this register, the serial-bus slave address must be programmed
with both the 7-bit slave address and the read/write indicator bit, and bit 5 (REQBUSY) in the serial-bus control and
status register (see Section 4.48) must be polled until clear. Then the contents of the serial-bus data register are valid
read data from the serial-bus interface. See Table 4−22 for a complete description of the register contents.
Bit 7 6 5 4 3 2 1 0
Name Serial-bus index
Type RW RW RW RW RW RW RW RW
Default 0 0 0 0 0 0 0 0
Register: Serial-bus index
Offset: B1h (function 0)
Type: Read/Write
Default: 00h
Table 4−22. Serial-Bus Index Register Description
BIT SIGNAL TYPE FUNCTION
7−0 SBINDEX RW Serial-bus index. This bit field represents the byte address in a read or write transaction on the serial interface.
4.47 Serial-Bus Slave Address Register
The serial-bus slave address register is for programmable serial-bus byte read and write transactions. To write a byte,
the serial-bus data register must be programmed with the data, the serial-bus index register must be programmed
with the byte address, and this register must be programmed with both the 7-bit slave address and the read/write
indicator bit.
On byte reads, the byte address is programmed into the serial bus index register, this register must be programmed
with both the 7-bit slave address and the read/write indicator bit, and bit 5 (REQBUSY) in the serial-bus control and
status register (PCI offset B3h, see Section 4.48) must be polled until clear. Then the contents of the serial-bus data
register are valid read data from the serial-bus interface. See Table 4−23 for a complete description of the register
contents.
Bit 7 6 5 4 3 2 1 0
Name Serial-bus slave address
Type RW RW RW RW RW RW RW RW
Default 0 0 0 0 0 0 0 0
Register: Serial-bus slave address
Offset: B2h (function 0)
Type: Read/Write
Default: 00h
Table 4−23. Serial-Bus Slave Address Register Description
BIT SIGNAL TYPE FUNCTION
7−1 SLAVADDR RW
Serial-bus slave address. This bit field represents the slave address of a read or write transaction on the
serial interface.
0 RWCMD RW
Read/write command. Bit 0 indicates the read/write command bit presented to the serial bus on byte read
and write accesses.
0 = A byte write access is requested to the serial bus interface.
1 = A byte read access is requested to the serial bus interface.