X76F041 Datasheet, PDF (8/21 Pages) Xicor Inc. – PASS TM SecureFlash

X76F041
ACK Polling
Once a stop condition is issued to indicate the end of the
host’s write sequence, the X76F041 initiates the internal
nonvolatile write cycle. In order to take advantage of the
typical 5ms write cycle, ACK polling can be initiated
immediately. This involves issuing the Start condition fol-
lowed by the new command code of eight bits (1st byte of
the protocol). If the X76F041 is still busy with the nonvol-
atile 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. Refer to the following flow:
ACK Polling Sequence
WRITE SEQUENCE
COMPLETED
ENTER ACK POLLING
ISSUE
A START
After a password sequence, there is always a nonvolatile
write cycle. In order to continue the transaction, the
X76F041 requires the master to perform an ACK polling
with the specific code of C0h. As with regular acknowl-
edge polling the user can either time out for 10ms, and
then issue the ACK polling once, or continuously loop as
described in the flow.
As with regular acknowledge polling, if the user chooses
to loop, then as long as the nonvolatile write cycle is
active, a no ACK will be issued in response to each poll-
ing cycle.
If the password that was inserted was correct, then an
“ACK” will be returned once the nonvolatile write cycle is
over, in response to the ACK polling cycle immediately
following it.
If the password that was inserted was incorrect, then a
“no ACK” will be returned even if the nonvolatile write
cycle is over. Therefore, the user cannot be certain that
the password is incorrect until the 10ms write cycle time
has elapsed.
ISSUE NEW
COMMAND CODE
(1ST BYTE)
ACK
RETURNED
NO ACK (SDA HIGH)
YES (SDA LOW)
PROCEED
7002 ILL F12A
Figure 7. Acknowledge Polling
SCL
8th clk.
of 8th
‘ACK’
clk
8th
clk
pwd. byte
SDA
‘ACK’
8th
bit
START
condition
8
ACK
clk
ACK or
no ACK
7002 ILL F11