Actel Fusion Mixed-Signal FPGAs
Unprotect Page Operation
An Unprotect Page operation will clear the protection for a page addressed on the ADDR input. It
is initiated by setting the UNPROTECTPAGE signal on the interface along with the page address on
ADDR.
If the page is not in the Page Buffer, the Unprotect Page operation will copy the page into the Page
Buffer. The Copy Page operation occurs only if the current page in the Page Buffer is not Page Loss
Protected.
The waveform for an Unprotect Page operation is shown in Figure 2-41.
CLK
UNPROTECTPAGE
Page
ADDR[17:0]
BUSY
STATUS[1:0]
Valid
Figure 2-41 • FB Unprotected Page Waveform
The Unprotect Page operation can incur the following error conditions:
1. If the copy of the page to the Page Buffer determines that the page has a single-bit
correctable error in the data, it will report a STATUS = '01'.
2. If the address on ADDR does not match the address of the Page Buffer, PAGELOSSPROTECT is
asserted, and the Page Buffer has been modified, then STATUS = '11' and the addressed
page is not loaded into the Page Buffer.
3. If the copy of the page to the Page Buffer determines that at least one block in the page has
a double-bit uncorrectable error, STATUS = '10' and the Page Buffer will contain the
corrupted data.
Discard Page Operation
If the contents of the modified Page Buffer have to be discarded, the DISCARDPAGE signal should
be asserted. This command results in the Page Buffer being marked as unmodified.
The timing for the operation is shown in Figure 2-42. The BUSY signal will remain asserted until the
operation has completed.
CLK
DISCARDPAGE
BUSY
Figure 2-42 • FB Discard Page Waveform
Preliminary v1.7
2-53
ACTEL [ Actel Corporation ]
