X76F101 Datasheet, PDF (5/17 Pages) Xicor Inc. – Secure SerialFlash

X76F101
followed by the new command code of 8 bits (1st byte of
the protocol.) If the X76F101 is still busy with the
nonvolatile write operation, it will issue a “no-ACK” in
response. If the nonvolatile write operation has
completed, an “ACK” will be returned and the host can
then proceed with the rest of the protocol.
Data ACK Polling Sequence
WRITE SEQUENCE
COMPLETED
ENTER ACK POLLING
ISSUE START
ISSUE NEW
COMMAND
CODE
ACK
NO
RETURNED?
YES
PROCEED
After the password sequence, there is always a nonvola-
tile write cycle. This is done to discourage random
guesses of the password if the device is being tampered
with. In order to continue the transaction, the X76F101
requires the master to perform a password ACK polling
sequence with the specific command code of 55h. As
with regular Acknowledge polling the user can either time
out for 10ms, and then issue the ACK polling once, or
continuously loop as described in the flow.
If the password that was inserted was correct, then an
“ACK” will be returned once the nonvolatile cycle in
response to the passwrod ACK polling sequence is over.
If the password that was inserted was incorrect, then a
“no ACK” will be returned even if the nonvolatile cycle is
over. Therefore, the user cannot be certain that the pass-
word is incorrect until the 10ms write cycle time has
elapsed.
Password ACK Polling Sequence
PASSWORD LOAD
COMPLETED
ENTER ACK POLLING
ISSUE START
ISSUE
PASSWORD
ACK COMMAND
ACK
NO
RETURNED?
YES
PROCEED
READ OPERATIONS
Read operations are initiated in the same manner as
write operations but with a different command code.
Sector Read
With sector read, a sector address is supplied with the
read command. Once the password has been
acknowledged data may be read from the sector. An
acknowledge must follow each 8-bit data transfer. A read
operation always begins at the first byte in the sector, but
may stop at any time. Random accesses to the array are
not possible. Continuous reading from the array will
return data from successive sectors. After reading the
last sector in the array, the address is automatically set to
the first sector in the array and data can continue to be
read out. After the last bit has been read, a stop condition
is generated without sending a preceding acknowledge.
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