M1AFS250-FGG256I Actel Corporation, M1AFS250-FGG256I Datasheet - Page 68

• Manufacturer Part Number: M1AFS250-FGG256I
• Description: Actel Fusion Family Of Mixed Signal Fpgas
• Manufacturer: Actel Corporation

Device Architecture
Figure 2-40 • Read Next Waveform (Non-Pipe Mode, 32-bit access)
Figure 2-41 • Read Next WaveForm (Pipe Mode, 32-bit access)
2- 52
DATAWIDTH[1:0]
STATUS[1:0]
READNEXT
ADDR[17:0]
STATUS[1:0]
RD[31:0]
READNEXT
ADDR[17:0]
BUSY
RD[31:0]
REN
CLK
BUSY
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:
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
and
REN
CLK
•
•
•
•
•
Figure
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.
0
0
0
2-41.
A0
A0
A1
A1
S0
D0
R e visio n 1
D1
S1
D0
S0
A2
S2
D2
D1
S1
A3
A2
D3
S3
D2
S2
A4
A3
0
0
S3
D3
A4
A5
D4
S4
0
0
S5
D5
A6
A5
D4
S4
D6
S6
A7
D5
S5
S7
D7
A6
A8
D6
S6
0
0
A7
Figure 2-40
A9
S7
D7
D8
S8
A8
S9
D9
0
0