X76F100PI datasheet(5/16 Pages) XICOR

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X76F100

Characteristics subject to change without notice.

5 of 16

REV 1.0 6/22/00

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Data ACK Polling Sequence

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.

Password ACK Polling Sequence

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.

ACK

returned?

Issue New

Command Code

Write Sequence

Completed

Enter ACK Polling

Issue START

YES

PROCEED

ACK

returned?

Issue Password

ACK Command

Password Load

Completed

Enter ACK Polling

Issue START

YES

PROCEED

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