28F008SA
command (20H) is first written to the Command User
Interface, followed by the Erase Confirm command
(D0H). These commands require both appropriate
sequencing and an address within the block to be
erased to FFH. Block preconditioning, erase and
verify are all handled internally by the Write State
Machine, invisible to the system. After the two-com-
mand erase sequence is written to it, the 28F008SA
automatically outputs Status Register data when
read (see Figure 8; Block Erase Flowchart). The
CPU can detect the completion of the erase event
Intelligent Identifier Command
The 28F008SA contains an Intelligent Identifier op-
eration, initiated by writing 90H into the Command
User Interface. Following the command write, a read
cycle from address 00000H retrieves the manufac-
turer code of 89H. A read cycle from address
00001H returns the device code of A2H. To termi-
nate the operation, it is necessary to write another
valid command into the register. Like the Read Array
command, the Intelligent Identifier command is func-
Ý
by analyzing the output of the RY/BY pin, or the
WSM Status bit of the Status Register.
e
tional when V
V
PPL
or V
.
PP
PPH
When erase is completed, the Erase Status bit
should be checked. If erase error is detected, the
Status Register should be cleared. The Command
User Interface remains in Read Status Register
mode until further commands are issued to it.
Read Status Register Command
The 28F008SA contains a Status Register which
may be read to determine when a byte write or block
erase operation is complete, and whether that oper-
ation completed successfully. The Status Register
may be read at any time by writing the Read Status
Register command (70H) to the Command User In-
terface. After writing this command, all subsequent
read operations output data from the Status Regis-
ter, until another valid command is written to the
Command User Interface. The contents of the
Status Register are latched on the falling edge of
This two-step sequence of set-up followed by execu-
tion ensures that memory contents are not acciden-
tally erased. Also, reliable block erasure can only
e
voltage, memory contents are protected against era-
occur when V
V
. In the absence of this high
PPH
PP
e
sure. If block erase is attempted while V
V
,
PP
PPL
the V Status bit will be set to ‘‘1’’. Erase attempts
PP
while V
Ý
Ý
OE or CE , whichever occurs last in the read cy-
cle. OE or CE must be toggled to V before
k
k
V V
PP
produce spurious results
PPL
PPH
Ý
Ý
and should not be attempted.
IH
further reads to update the Status Register latch.
The Read Status Register command functions when
Erase Suspend/Erase Resume
Commands
e
V
PP
V
PPL
or V
.
PPH
The Erase Suspend command allows block erase
interruption in order to read data from another block
of memory. Once the erase process starts, writing
the Erase Suspend command (B0H) to the Com-
mand User Interface requests that the WSM sus-
pend the erase sequence at a predetermined point
in the erase algorithm. The 28F008SA continues to
output Status Register data when read, after the
Erase Suspend command is written to it. Polling the
WSM Status and Erase Suspend Status bits will de-
termine when the erase operation has been sus-
Clear Status Register Command
The Erase Status and Byte Write Status bits are set
to ‘‘1’’s by the Write State Machine and can only be
reset by the Clear Status Register Command. These
bits indicate various failure conditions (see Table 4).
By allowing system software to control the resetting
of these bits, several operations may be performed
(such as cumulatively writing several bytes or eras-
ing multiple blocks in sequence). The Status Regis-
ter may then be polled to determine if an error oc-
curred during that sequence. This adds flexibility to
the way the device may be used.
Ý
pended (both will be set to ‘‘1’’). RY/BY will also
transition to V
.
OH
Additionally, the V Status bit (SR.3) MUST be re-
PP
At this point, a Read Array command can be written
to the Command User Interface to read data from
blocks other than that which is suspended. The only
other valid commands at this time are Read Status
Register (70H) and Erase Resume (D0H), at which
time the WSM will continue with the erase process.
The Erase Suspend Status and WSM Status bits of
the Status Register will be automatically cleared and
set by system software before further byte writes or
block erases are attempted. To clear the Status
Register, the Clear Status Register command (50H)
is written to the Command User Interface. The Clear
e
Status Register command is functional when V
.
PPH
PP
V
or V
PPL
Ý
RY/BY will return to V . After the Erase Resume
OL
command is written to it, the 28F008SA automatical-
ly outputs Status Register data when read (see Fig-
Erase Setup/Erase Confirm
Commands
ure 9; Erase Suspend/Resume Flowchart).
V
PP
while the 28F008SA is in Erase
Erase is executed one block at a time, initiated by a
two-cycle command sequence. An Erase Setup
must remain at V
Suspend.
PPH
13
INTEL [ INTEL ]
