USB5534B datasheet(37/73 Pages) MICROCHIP

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DS00001681C-page 37

USB5534B

5.6.1

ACCESSING RUNTIME REGISTERS

The Configuration Register Access operation allows the SMBus Master to read or write to the internal registers of the

hub. When the Configuration Register Access command is sent the hub will interpret the memory starting at offset 00h

as follows:

5.6.1.1

Configuration Register Write Example

The following example shows how the SMBus messages will be formatted to set the VID of the hub to a custom value,

AA55h.

Write data to the memory of the hub:

Execute the Configuration Register Access command:

TABLE 5-13:

MEMORY FORMAT FOR CONFIGURATION REGISTER ACCESS

RAM Address

Description

Notes

0000h

Direction

0 = Register Write, 1 = Register Read.

0001h

Data Length

Number of bytes to Read/Write when executing the command.

0002h

Configuration

Address MSB

The upper byte of the 16-bit configuration register address.

0003h

Configuration

Address LSB

The lower byte of the 16-bit configuration register address.

0004h

Data1

The first byte of data to write to or read from the Configuration Address.

...

0004h+N

DataN

The Nth byte of data to write to or read from the Configuration Address, N

is equal to the Data Length.

TABLE 5-14:

EXAMPLE SMBUS WRITE COMMAND

Byte

Value

Comment

5Ah

Address plus write bit.

00h

Memory address 0000h.

00h

Memory address 0000h.

06h

Number of bytes to write to memory.

00h

Write Configuration Register.

02h

Writing two data bytes.

30h

VID is in register 3000h.

00h

VID is in register 3000h.

55h

LSB of Vendor ID AA55h.

AAh

MSB of Vendor ID AA55h.

TABLE 5-15:

CONFIGURATION REGISTER ACCESS COMMAND

Byte

Value

Comment

5Ah

Address plus write bit.

99h

Command 9937h.

37h

Command 9937h.

00h

Command Completion.

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