There are three primary modes of operation for the
X76F041; READ, WRITE and CONFIGURATION. The
READ and WRITE modes may be performed with or
without an 8-byte password. The CONFIGURATION
mode always requires an 8-byte password.
The basic method of communication is established by
ﬁrst enabling the device (CS LOW), generating a start
condition and then transmitting a command and address
ﬁeld followed by the correct password (if conﬁgured to
require a password). All parts will be shipped from the
factory in the non-password mode. The user must per-
form an ACK Polling routine to determine the validity of
the password and start the data transfer (see Acknowl-
edge Polling). Only after the correct password is
accepted and an ACK Polling has been performed can
the data transfer occur.
To ensure correct communication, RST must remain
LOW under all conditions except when initiating a
“Response to Reset sequence”.
Figure 1. X76F041 Device Operation
COMMAND+HIGH ORDER ADDRESS
LOW ORDER ADDRESS / CONFIGURATION INSTRUCTION
LOAD 8–BYTE PASSWORD
VERIFY PASSWORD ACCEPTANCE BY USE
OF ACK POLLING (IF APPLICABLE)
READ / WRITE
7002 ILL F03
Data is transferred in 8-bit segments, with each transfer
being followed by an ACK, generated by the receiving
If the X76F041 is in a nonvolatile write cycle a “no ACK”
(SDA HIGH) response will be issued in response to load-
ing of the command + high order address byte. If a stop
condition is issued prior to the nonvolatile write cycle the
write operation will be terminated and the part will reset
and enter into a standby mode.
The basic sequence is illustrated in Figure 1.
After each transaction is completed, the X76F041 will
reset and enter into a standby mode. This will also be the
response if an attempt is made to access any limited
The three passwords, Read, Write and Conﬁguration
are stored in three 64 bit Write Only registers as illus-
trated in ﬁgure 2.
Figure 2. Password Registers
64 BIT WRITE PASSWORD
64 BIT READ PASSWORD
64 BIT CONFIGURATION PASSWORD
7002 ILL F04
Five 8-Bit conﬁguration registers are used to conﬁgure
the X76F041. These are shown in ﬁgure 3.
Figure 3. Configuration Registers
ACR1 ACR2 CR RR RC RES RES RES
ARRAY CONTROL REGISTER 2
ARRAY CONTROL REGISTER 1
7002 ILL F04B