6.3.1

Random address read

A dummy write is first performed to load the address into this address counter (as shown in Figure 8) 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.

6.3.2

Current address read

For the current address read operation, following a start condition, the bus master only sends a device select

code with the R/W 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 8, without acknowledging the byte.

Note that the address counter value is defined by instructions accessing either the memory or the identification

page. When accessing the identification page, the address counter value is loaded with the identification page

byte location, therefore the next current address read in the memory uses this new address counter value. When

accessing the memory, it is safer to use the random address read instruction (this instruction loads the address

counter with the byte location to read in the memory) instead of the current address read instruction.

6.3.3

Sequential read

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 9.

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.

M24128X-FCU

Read operations on memory array

DS12680 - Rev 2

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