STTS424E02 datasheet(34/51 Pages) STMICROELECTRONICS

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SPD EEPROM operation

STTS424E02

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5.6

Read operations - SPD

Read operations are performed independently of whether hardware or software protection

has been set.

The device has an internal address counter which is incremented each time a byte is read.

5.6.1

Random address read - SPD

A dummy Write is first performed to load the address into this address counter (as shown in

Figure 14) but without sending a Stop condition. Then, the bus master sends another Start

condition, and repeats the Device Select Code, with the RW bit set to 1. The device

acknowledges this, and outputs the contents of the addressed byte. The bus master must

not acknowledge the byte, and terminates the transfer with a Stop condition.

5.6.2

Current address read - SPD

For the Current Address Read operation, following a Start condition, the bus master only

sends a Device Select Code with the RW bit set to 1. The device acknowledges this, and

outputs the byte addressed by the internal address counter. The counter is then

incremented. The bus master terminates the transfer with a Stop condition, as shown in

Figure 14, without acknowledging the byte.

5.6.3

Sequential read - SPD

This operation can be used after a Current Address Read or a Random Address Read. The

bus master does acknowledge the data byte output, and sends additional clock pulses so

that the device continues to output the next byte in sequence. To terminate the stream of

bytes, the bus master must not acknowledge the last byte, and must generate a Stop

condition, as shown in Figure 14.

The output data comes from consecutive addresses, with the internal address counter

automatically incremented after each byte output. After the last memory address, the

address counter ‘rolls-over’, and the device continues to output data from memory address

00h.

5.6.4

Acknowledge in read mode

For all Read commands, the device waits, after each byte read, for an acknowledgment

during the 9th bit time. If the bus master does not drive Serial Data (SDA) Low during this

time, the device terminates the data transfer and switches to its Standby mode.

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