M58PR256J datasheet(58/114 Pages) STMICROELECTRONICS

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Read modes

M58PR256J, M58PR512J

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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 Configuration Register section 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, that is 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 so 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 will be valid, all subsequent data will be

indeterminate.

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 150ns, the device automatically switches to the Automatic Standby

mode. In this condition 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 28: 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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