AT85C51SND3Bx
Bit
Bit
Number
Mnemonic Description
Block Size Bits
Write following value to specify the number of pages per block. This information
is needed by the controller for the block protection management.
1-0
BSIZE1:0
0 0: 32 pages per block
0 1: 64 pages per block
1 0: 128 pages per block
1 1: 256 pages per block
Reset Value = 0000 0000b
Specific Action
As soon as the NFC is configured, the NFC is ‘idle’, i.e. ready for operation and its run-
ning status flag NFRUN in NFSTA is cleared. The controller is ready to accept events,
typically to prepare a page for read or write.
As long as the NFC remains in the running state (NFRUN flag set), any attempt to new
event will lead to an ILLEGAL interrupt.
Here is the list of the possible events:
Writing in the NFACT register as detailed in Table 192 launches a specific action:
•
•
•
•
•
select a device,
begin a read data transfer (thus the spare zone will be checked),
begin a write data transfer (thus the spare zone will be set),
stop a data transfer before the end of a page,
force CE low.
Table 192. Action Decoding
EXT1:0
ACT2:0
Launched Action
x
x
0
0
0
0
1
No action
Device selection.
DEV
0
The device number is selected by EXT.
x
x
x
x
0
0
1
1
1
1
1
1
0
0
1
1
0
1
0
1
0
1
Read session.
Write session.
x
CELOW
Selected NFCE signal assertion.
Data transfer stop.
x
x
A8
x
A9
x
Column address extension.
Reserved for future use.
Device Selection
This command selects the device which will receive the next incoming events. The
device number is memorized until a new device selection action is performed.
DEV is the device number. SMC shall always be connected on device 3. Table 193
summarizes the possible configurations: if DEV is a device that does not comply with
the configuration allowed, an illegal interrupt is triggered.
171
7632A–MP3–03/06
ATMEL [ ATMEL ]
