X76F400 Datasheet, PDF (4/14 Pages) IC MICROSYSTEMS – Secure SerialFlash

X76F400
Figure 3. Definition of Start and Stop Conditions
SCL
SDA
START Condition
Table 1. X76F400 Instruction Set
Command After Start
1 S₅ S₄ S₃ S₂ S₁ S₀0
1 S₅ S₄ S₃ S₂ S₁ S₀ 1
11111100
11111110
01010101
STOP Condition
Command Description
Sector Write
Sector Read
Change Write Password
Change Read Password
Password ACK Command
Password Used
Write
Read
Write
Write
None
Illegal command codes will be disregarded. The part will
respond with a “no-ACK” to the illegal byte and
then return to the standby mode. All write/read operations
require a password.
PROGRAM OPERATIONS
Sector Write
The sector write mode requires issuing the 8-bit write
command followed by the password and then the data
bytes transferred as illustrated in Figure 4. The write
command byte contains the address of the sector to be
written. Data is written starting at the first address of a
sector and 8 bytes must be transferred. After the last
byte to be transferred is acknowledged, a stop condition is
issued which starts the nonvolatile write cycle. If
more or less than 8 bytes are transferred, the data in the
sector remains unchanged.
ACK Polling
Once a stop condition is issued to indicate the end of the
host’s write sequence, the X76F400 initiates the
internal nonvolatile write cycle. In order to take advantage of
the typical 5ms write cycle, ACK polling can
begin immediately. This involves issuing the start condition
followed by the new command code of 8 bits
(first byte of the protocol). If the X76F400 is still busy
with the nonvolatile write operation, it will issue a “no-
ACK” in response. If the nonvolatile write operation is
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
REV 1.0 7/5/00
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