All Bus Write operations to the memory are inter-
preted by the Command Interface. Commands
consist of one or more sequential Bus Write oper-
ations. An internal Program/Erase Controller han-
dles all timings and verifies the correct execution
of the Program and Erase commands. The Pro-
gram/Erase Controller provides a Status Register
whose output may be read at any time, to monitor
the progress of an operation, or the Program/
Erase states. See Appendix D, Table 30, Write
State Machine Current/Next, for a summary of the
The Command Interface is reset to Read mode
when power is first applied, when exiting from Re-
set or whenever VDD is lower than VLKO. Com-
mand sequences must be followed exactly. Any
invalid combination of commands will reset the de-
vice to Read mode. Refer to Table 3, Commands,
in conjunction with the text descriptions below.
Read Memory Array command
The Read command returns the memory to its
Read mode. One Bus Write cycle is required to is-
sue the Read Memory Array command and return
the memory to Read mode. Subsequent read op-
erations will read the addressed location and out-
put the data. When a device Reset occurs, the
memory defaults to Read mode.
Read Status Register Command
The Status Register indicates when a program or
erase operation is complete and the success or
failure of the operation itself. Issue a Read Status
Register command to read the Status Register’s
contents. Subsequent Bus Read operations read
the Status Register, at any address, until another
command is issued. See Table 7, Status Register
Bits, for details on the definitions of the bits.
The Read Status Register command may be is-
sued at any time, even during a Program/Erase
operation. Any Read attempt during a Program/
Erase operation will automatically output the con-
tent of the Status Register.
Read Electronic Signature Command
The Read Electronic Signature command reads
the Manufacturer and Device Codes.
The Read Electronic Signature command consists
of one write cycle, a subsequent read will output
the Manufacturer or the Device Code depending
on the levels of A0. The Manufacturer Code is out-
put when the address line A0 is at VIL, the Device
Code is output when A0 is at VIH. Addresses A1-
A7 must be kept to VIL, other addresses are ig-
nored. The codes are output on DQ0-DQ7 with
DQ8-DQ15 at 00h. (see Table 4)
Read CFI Query Command
The Read Query Command is used to read data
from the Common Flash Interface (CFI) Memory
Area, allowing programming equipment or appli-
cations to automatically match their interface to
the characteristics of the device.
One Bus Write cycle is required to issue the Read
Query Command. Once the command is issued
subsequent Bus Read operations read from the
Common Flash Interface Memory Area. See Ap-
pendix B, Common Flash Interface, Tables 24, 25,
26, 27, 28 and 29 for details on the information
contained in the Common Flash Interface memory
Block Erase Command
The Block Erase command can be used to erase
a block. It sets all the bits within the selected block
to ’1’. All previous data in the block is lost. If the
block is protected then the Erase operation will
abort, the data in the block will not be changed and
the Status Register will output the error.
Two Bus Write cycles are required to issue the
s The first bus cycle sets up the Erase command.
s The second latches the block address in the
internal state machine and starts the Program/
If the second bus cycle is not Write Erase Confirm
(D0h), Status Register bits b4 and b5 are set and
the command aborts.
Erase aborts if Reset turns to VIL. As data integrity
cannot be guaranteed when the Erase operation is
aborted, the block must be erased again.
During Erase operations the memory will only ac-
cept the Read Status Register command and the
Program/Erase Suspend command, all other com-
mands will be ignored. Typical Erase times are
given in Table 6, Program, Erase Times and Pro-
gram/Erase Endurance Cycles.
See Appendix C, Figure 23, Erase Flowchart and
Pseudo Code, for the flowchart for using the Erase
The memory array can be programmed word-by-
word. Two bus write cycles are required to issue
the Program command.
s The first bus cycle sets up the Program
s The second latches the Address and the Data to
be written and starts the Program/Erase
During Program operations the memory will only
accept the Read Status Register command and
the Program/Erase Suspend command. All other