X76F102 datasheet(5/18 Pages) XICOR

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X76F102

the new command code of 8 bits (1st byte of the proto-

col.) If the X76F102 is still busy with the nonvolatile write

operation, it will issue a “no-ACK” in response. If the non-

volatile write operation has completed, an “ACK” will be

returned and the host can then proceed with the rest of

the protocol.

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 X76F102

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.

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 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.

Data ACK Polling Sequence

ACK

RETURNED?

ISSUE NEW

COMMAND

CODE

Write sequence completed

Enter ACK Polling

ISSUE START

YES

PROCEED

Password ACK Polling Sequence

ACK

RETURNED?

ISSUE

PASSWORD

ACK COMMAND

PASSWORD LOAD

COMPLETED

ENTER ACK POLLING

ISSUE START

YES

PROCEED

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