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L99SD01-E

I2C protocol description

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4.8

Read operation

READ command in L99SD01-E is used to read data contained into volatile memory. There

are essentially two different Read operation modes: Current Read and Random Read.

In Random READ mode a dummy write is first performed to load the address into the

address counter, then without sending a STOP condition, the Master sends another START

condition, and repeats the slave address, with the R/W bit set to ‘1’ (READ). At this point

slave acknowledges and starts sending data output from the addressed register. One or

more bytes can be sent to master. L99SD01-E stops sending data when it receives a NACK

signal from master. At this point master can decide to stop transmission by sending a STOP

condition or to generate a repeated START condition to start communication with another

slave. At the end of communication internal address counter is incremented automatically,

to point to the next byte address after the last one that was read.

In Current READ mode, following a START condition, the master sends a slave address

with a R/W bit set to ‘1’. At this point slave acknowledges and starts sending data output

from the register addressed by the internal counter. One or more bytes can be sent to

master. L99SD01-E stops sending data when it receives a NACK signal from master. At this

point master can decide to stop transmission by sending a STOP condition or to generate a

repeated START condition to start communication with another slave.

Figure 17. Current READ command

A

S

SLAVE ADDRESS

R/W

A

A

DATA

P

From master to slave

From slave to master

A = acknowledge (SDA LOW)

A = not acknowledge (SDA HIGH)

S = START condition

P = STOP condition

‘1’ (read)

Example: Read two registers values for L99SD01-E with enable chip = 1. Internal register counter is pointing to register 7 (0:7)

S

0 1 0 1 0 0 1

1

A

Phase1 time max

A

P

Ipeak current

DATA

A

DATA

After read operation internal register counter is pointing to register 1

A