M58LW064 datasheet(14/53 Pages) STMICROELECTRONICS

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M58LW064A, M58LW064B

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M8 Valid Data Ready R Signal Configuration.

The Valid Data Ready R output signal indicates

when valid data is on the data outputs synchro-

nous with the valid burst clock egde. It can be as-

serted by the device synchronously with the valid

clock edge or one clock cycle before.

M7 Burst Type.

Accesses within a given burst may be pro-

grammed to be either Sequential or Interleaved.

This is referred to as the burst type and is selected

by the Burst Configuration Register M7 bit. The ac-

cess order within a burst is determined by the

burst length, the burst type and the starting ad-

dress (See Table 8).

M6 Valid Clock Edge Configuration.

All the synchronous operations such as Burst

Read, Output Data or Ready signal validation can

be synchronized on the valid rising or on the falling

edge of the Burst Clock signal K.

M2 - M0 Burst Length.

Synchronous reads have a programmable burst

length, set using the M2 - M0 bits of the Burst Con-

figuration Register. The burst length corresponds

to the maximum number of Words or Double-

Words that can be output. Burst lengths of 1, 2, 4

or 8 are available for both the Sequential and In-

terleaved burst types, and a continuous burst is

available for the Sequential type. The burst length

of 8 is not available in the x32 configuration.

When a Read command is issued, a block of

Words or Double-Words equal to the burst length

is selected. All accesses for that burst take place

within this block, meaning that the burst wraps

within the burst block if a boundary is reached.

If a Continuous Burst Read has been initiated the

device will output data synchronously. Depending

on the starting address of the read, the device ac-

tivates the Valid Data Ready R output to indicate

that it needs a delay to complete the internal read

operation before outputing data. If the starting ad-

dress is aligned to a four Word boundary the con-

tinuous burst mode will run without activating the

Valid Data Ready R output. If the starting address

is not aligned to a four Word boundary, Valid Data

Ready R is activated at the beginning of the con-

tinuous burst read to indicate that the device

needs an internal delay to read the content of the

four successive words in the array.

Pipelined Burst Read.

An overlapping Burst Read operation is possible.

That is, the address and data phases of consecu-

tive synchronous read operations can be over-

lapped by several clock cycles. This is done by

applying a pulse on Latch Enable L input to latch a

new address before the completion of the data

output of the current cycle. This reduces or avoids

wait-states in the data output for the burst read

mode. The minimum clock edge number for the

following read sequence must be six before the

last data output of the previous read cycle. The

pipelined burst read mode is available in the x16

organisation for both burst length definitions of

four and eight, and in the x32 organisation for the

burst length of four. It is not possible for a burst

length of one or two.

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