AFS090 datasheet(68/334 Pages) MICROSEMI

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Device Architecture

2- 52

R e visio n 2

Read Next Operation

The Read Next operation is a feature by which the next block relative to the block in the Block Buffer is

read from the FB Array while performing reads from the Block Buffer. The goal is to minimize wait states

during consecutive sequential Read operations.

The Read Next operation is performed in a predetermined manner because it does look-ahead reads.

The general look-ahead function is as follows:

•

Within a page, the next block fetched will be the next in linear address.

•

When reading the last data block of a page, it will fetch the first block of the next page.

•

When reading spare pages, it will read the first block of the next sector's spare page.

•

Reads of the last sector will wrap around to sector 0.

•

Reads of Auxiliary blocks will read the next linear page's Auxiliary block.

When an address on the ADDR input does not agree with the predetermined look-ahead address, there

is a time penalty for this access. The FB will be busy finishing the current look-ahead read before it can

start the next read. The worst case is a total of nine BUSY cycles before data is delivered.

The Non-Pipe Mode and Pipe Mode waveforms for Read Next operations are illustrated in Figure 2-40

and Figure 2-41.

Figure 2-40 • Read Next Waveform (Non-Pipe Mode, 32-bit access)

Figure 2-41 • Read Next WaveForm (Pipe Mode, 32-bit access)

CLK

REN

READNEXT

ADDR[17:0]

DATAWIDTH[1:0]

BUSY

STATUS[1:0]

RD[31:0]

S0S1S2

S5S6

0D0

CLK

REN

READNEXT

ADDR[17:0]

BUSY

STATUS[1:0]

RD[31:0]

0D0

0D4

AFS090 Datasheet(PDF) 68 Page - Microsemi Corporation

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