M58PR256LE datasheet(59/119 Pages) STMICROELECTRONICS

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M58PR256LE, M58PR512LE, M58PR001LE

Read modes

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Read modes

Read operations can be performed in two different ways depending on the settings in the

Configuration Register. If the clock signal is ‘don’t care’ for the data output, the read

operation is asynchronous. If the data output is synchronized with clock, the read operation

is synchronous.

The read mode and format of the data output are determined by the Configuration Register.

(See Section 7: Configuration Register for details). All banks support both asynchronous

and synchronous read operations.

10.1

Asynchronous read mode

In asynchronous read operations the clock signal is ‘don’t care’. The device outputs the data

corresponding to the address latched, such as the memory array, Status Register, common

Flash interface or electronic signature, depending on the command issued. CR15 in the

Configuration Register must be set to ‘1’ for asynchronous operations.

Asynchronous read operations can be performed in two different ways, asynchronous

random access read and asynchronous page read. Only asynchronous page read takes full

advantage of the internal page storage, therefore, different timings are applied.

In asynchronous read mode a page of data is internally read and stored in a page buffer.

The page has a size of 16 words and is addressed by address inputs A0, A1, A2 and A3.

During the page access, Amax-A4 and L must remain stable.

The first read operation within the page has a longer access time (tAVQV, Random access

time); subsequent reads within the same page have much shorter access times (tAVQV1,

page access time). If the page changes then the normal, longer timings apply again.

Read operations to read non-array data (Status Register, electronic signature, CFI) should

be performed in asynchronous single word mode. If the asynchronous page mode is used to

read non-array data, only the first output data is valid and all subsequent data is not

accurately determined.

The asynchronous page read mode is not available in the EFA.

The device features an Automatic Standby mode. During asynchronous read operations,

after a bus inactivity of 150 ns, the device automatically switches to automatic standby

mode. In this state the power consumption is reduced to the standby value and the outputs

are still driven.

In asynchronous read mode, the Wait signal is always de-asserted.

See Table 29: Asynchronous read AC characteristics, Figure 10: Asynchronous random

access read AC waveforms and Figure 11: Asynchronous page read AC waveforms for

details.

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