Device Architecture
During a Program operation, the sector and page addresses on ADDR are compared with the
stored address for the page (and sector) in the Page Buffer. If there is a mismatch between the two
addresses, the Program operation will be aborted and an error will be reported on the STATUS
output.
It is possible to write the Page Buffer to a different page in memory. When asserting the PROGRAM
pin, if OVERWRITEPAGE is asserted as well, the FB will write the contents of the Page Buffer to the
sector and page designated on the ADDR inputs if the destination page is not Overwrite Protected.
A Program operation can be utilized to either modify the contents of the page in the flash memory
block or change the protections for the page. Setting the OVERWRITEPROTECT bit on the interface
while asserting the PROGRAM pin will put the page addressed into Overwrite Protect Mode.
Overwrite Protect Mode safeguards a page from being inadvertently overwritten during
subsequent Program or Erase operations.
Program operations that result in a STATUS value of '01' do not modify the addressed page. For all
other values of STATUS, the addressed page is modified.
Program errors include the following:
1. Attempting to program a page that is Overwrite Protected (STATUS = '01')
2. Attempting to program a page that is not in the Page Buffer when the Page Buffer has
entered Page Loss Protection Mode (STATUS = '01')
3. Attempting to perform a program with OVERWRITEPAGE set when the page addressed has
been Overwrite Protected (STATUS = '01')
4. The Write Count of the page programmed exceeding the Write Threshold defined in the
part specification (STATUS = '11')
5. The ECC Logic determining that there is an uncorrectable error within the programmed
page (STATUS = '10')
6. Attempting to program a page that is not in the Page Buffer when OVERWRITEPAGE is not
set and the page in the Page Buffer is modified (STATUS = '01')
7. Attempting to program the page in the Page Buffer when the Page Buffer is not modified
The waveform for a Program operation is shown in Figure 2-35.
CLK
PROGRAM
Page
ADDR[17:0]
OVERWRITEPAGE
OVERWRITEPROTECT
PAGELOSSPROTECT
BUSY
0
Valid
STATUS[1:0]
Figure 2-35 • FB Program Waveform
Note: OVERWRITEPAGE is only sampled when the PROGRAM or ERASEPAGE pins are asserted.
OVERWRITEPAGE is ignored in all other operations.
2-48
Preliminary v1.7
ACTEL [ Actel Corporation ]
