6402 datasheet(80/250 Pages) INTEL

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SMBus Interface

Intel® 6400/6402 Advanced Memory Buffer Datasheet

7.1.3.2

Configuration Register Write Protocol

Configuration writes are accomplished through a series of SMBus writes. As with

configuration reads, a write sequence is first used to initialize the Bus Number, Device,

Function, and Register Number for the configuration access. The writing of this

information can be accomplished through any combination of the supported SMBus

write commands (Block, Word or Byte).

On SMBus, there is no concept of byte enables. Therefore, the Register Number written

to the slave is assumed to be aligned to the length of the Internal Command. In other

words, for a Write Byte internal command, the Register Number specifies the byte

address. For a Write DWord internal command, the two least-significant bits of the

used to indicate the byte of interest.

After all the information is set up, the SMBus master initiates one or more writes which

sets up the data to be written. The final write (End bit is set) initiates an internal

configuration write. If an error occurred, the SMBus interface NACKs the last write

operation just before the stop bit.

Examples of configuration writes are illustrated below. For the definition of the diagram

conventions below, refer to the SMBus Specification, Rev. 2.0.

Figure 7-2. SMBus Configuration Read (Write Bytes / Read Bytes, PEC Enabled)

X011_XXX

W A

Cmd = 10010000

Reserved

PEC

A P

X011_XXX

W A

Cmd = 00010000

Device/Function

PEC

A P

X011_XXX

W A

Cmd = 01010000

PEC

X011_XXX

W A

Cmd = 00010000

X011_XXX

R A

Data[31:24]

X011_XXX

W A

Cmd = 00010000

X011_XXX

R A

Data[23:16]

PEC

N P

X011_XXX

W A

Cmd = 00010000

X011_XXX

R A

Data[15:8]

PEC

N P

X011_XXX

W A

Cmd = 01010000

X011_XXX

R A

Data[7:0]

PEC

N P

A P

PEC

N P

X011_XXX

W A

Cmd = 10010000

X011_XXX

R A

Status

PEC

N P

X011_XXX

W A

Cmd = 00010000

PEC

A P

Figure 7-3. SMBus Configuration Double Word Write (Block Write, PEC Enabled)

X011_XXX

Cmd = 11011110

Byte Count =8

Reserved

Device/Function

Reg Number[15:8]

Reg Number [7:0]

Data[31:24]

Data[23:16]

Data[16:8]

Data[7:0]

PEC

A P

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