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2023 Microchip Technology Inc.

DS20006768B-page 17

ZL40294

3.13 SMBus Block Read/Write

Read. After the client address is sent with the r/w condition bit set, the command byte is sent with the MSB = 0. The

client Ack’s the register index in the command byte. The host sends a repeat start function. After the client Ack’s this the

client sends the number of bytes it wants to transfer (>0 and <33). The host Ack’s each byte except the last and sends

a stop function.

FIGURE 3-11:

SMBUS BLOCK READ.

Write. After the client address is sent with the r/w condition bit not set, the command byte is sent with the MSB = 0. The

lower seven bits indicate what register to start the transfer at. If the command byte is 00h, the client device will be com-

patible with existing block mode client devices. The next byte of a write must be the count of bytes that the host will

transfer to the client device. The byte count must be greater than zero and less than 33. Following this byte are the data

bytes to be transferred to the client device. The client device always acknowledges each byte received. The transfer is

terminated after the client sends the Ack and the host sends a stop function.

FIGURE 3-12:

SMBUS BLOCK WRITE.

3.14 Side-Band Interface

Besides OE pins and SMBUS interface the device outputs can be enabled/disabled via a simple 3-wire serial interface

referred to as the Side-Band Interface (SBI).

This interface consists of the vDATA, vCLK and vSHFT_LD# pins. When the vSHFT_LD# pin is high, the rising edge of

vCLK can shift vDATA into the shift register. After shifting data, the falling edge of vSHFT_LD# clocks the shift register

contents to the Output register.