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DS20006768B-page 16

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2023 Microchip Technology Inc.

3.12 SMBus Byte Read/Write

Reading or writing a register in a SMBus client device in byte mode always involves specifying the register number.

Read. The standard byte read is as shown in Figure 11. It is an extension of the byte write. The write start condition is

repeated then the client device starts sending data and the host acknowledges it until the last byte is sent. The host

terminates the transfer with a NAK then a stop condition. For byte operation, the 2*7th bit of the command byte must be

set. For block operations, the 2*7th bit must be reset. If the bit is not set, the next byte must be the byte transfer count.

FIGURE 3-9:

SMBUS BYTE READ.

Write. Figure 12 illustrates a simple typical byte write. For byte operation the 2*7th bit of the command byte must be

set. For block operations, the 2*7th bit must be reset. If the bit is not set the next byte must be the byte transfer count.

The count can be between 1 and 32. It cannot be zero or exceed 32.

FIGURE 3-10:

SMBUS BYTE WRITE.

TABLE 3-3:

SMBUS ADDRESS TABLE

SA_1

SA_0

SMBus Address

L

L

D8

L

M

DA

L

H

DE

M

L

C2

M

M

C4

M

H

C6

H

L

CA

H

M

CC

H

H

CE