Texas Instruments PCI7611 Serial Bus Data Register, Serial Bus Index Register, Serial bus data

4.47 Serial Bus Data Register

The serial bus data register is for programmable serial bus byte reads and writes. This register represents the data when generating cycles on the serial bus interface. To write a byte, this register must be programmed with the data, the serial bus index register must be programmed with the byte address, the serial bus slave address must be programmed with the 7-bit slave address, and the read/write indicator bit must be reset.

On byte reads, the byte address is programmed into the serial bus index register, the serial bus slave address 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 (see Section 4.50) must be polled until clear. Then the contents of this 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 data

Type

RW

RW

RW

RW

RW

RW

RW

RW

Default

0

0

0

0

0

0

0

0

Register:

Serial bus data

Offset:

B0h (function 0)

Type:

Read/Write

Default:

00h

Table 4−22. Serial Bus Data Register Description

BIT

SIGNAL

TYPE

FUNCTION

7−0 ‡

SBDATA

RW

Serial bus data. This bit field represents the data byte in a read or write transaction on the serial interface.

On reads, the REQBUSY bit must be polled to verify that the contents of this register are valid.

‡These bits are cleared only by the assertion of GRST.

4.48 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 must be programmed with both the 7-bit slave address and the read/write indicator.

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 4.50) 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 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 4−23. 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.

‡ These bits are cleared only by the assertion of GRST.

4−35