X76F100 Datasheet, PDF (5/17 Pages) Xicor Inc. – 1K 128 x 8 Bit

X76F100
Data ACK Polling Sequence
Write Sequence
Completed
Enter ACK Polling
Issue START
Issue New
Command Code
Password ACK Polling Sequence
Password Load
Completed
Enter ACK Polling
Issue START
Issue Password
ACK Command
ACK
NO
returned?
YES
PROCEED
ACK
NO
returned?
YES
PROCEED
After the password sequence, there is always a nonvol-
atile write cycle. This is done to discourage random
guesses of the password if the device is being tam-
pered with. In order to continue the transaction, the
X76F100 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 password 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
password is incorrect until the 10ms write cycle time
has elapsed.
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 acknowl-
edged data may be read from the sector. An acknowl-
edge 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 auto-
matically 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.
REV 1.0 6/22/00
www.xicor.com
Characteristics subject to change without notice. 5 of 16