E
with altering memory contents are accessible via
the CUI.
28F002BC 2-MBIT BOOT BLOCK FLASH MEMORY
13
PRELIMINARY
The purpose of the Write State Machine (WSM) is
to automate the write and erasure of the device
completely. The WSM will begin operation upon
receipt of a signal from the CUI and will report
status back through the status register. The CUI will
handle the WE# interface to the data and address
latches, as well as system software requests for
status while the WSM is in operation.
3.1
Bus Operations
Flash memory reads, erases and writes in-system
via the local CPU. All bus cycles to or from the flash
memory conform to standard microprocessor bus
cycles. These bus operations are summarized in
Tables 2 and 4.
3.2
Read Operations
The 28F002BC has three user read modes: read
array, read intelligent identifier, and read status
register.
During power-up conditions, it takes a maximum of
600 ns from when V
CC
is at 4.5V to when valid data
is available at the outputs.
3.2.1
READ ARRAY
When RP# transitions from V
IL
(reset) to V
IH
, the
device will be in read array mode and will respond
to the read control inputs (CE#, OE#, and address
inputs) without any commands being written to the
CUI.
When the device is in read array mode, four control
signals must be manipulated to read data at the
outputs.
WE# must be logic high (V
IH
)
CE# must be logic low (V
IL
)
OE# must be logic low (V
IL
)
RP# must be logic high (V
IH
)
In addition, the address of the desired location must
be applied to the address pins. Refer to AC
Characteristics for the exact sequence and timing
of these signals.
If the device is not in read array mode, as would be
the case after a program or erase operation, the
Read Mode command (FFH) must be written to the
CUI before array reads can take place.
Table 2. 28F002BC Bus Operations
Mode
Notes
RP#
CE#
OE#
WE#
A
9
A
0
V
PP
DQ
0
–7
Read
1,2,3
V
IH
V
IL
V
IL
V
IH
X
X
X
D
OUT
Output Disable
V
IH
V
IL
V
IH
V
IH
X
X
X
High Z
Standby
V
IH
V
IH
X
X
X
X
X
High Z
Deep Power-Down
8
V
IL
X
X
X
X
X
X
High Z
Intelligent Identifier (Mfr)
4
V
IH
V
IL
V
IL
V
IH
V
ID
V
IL
X
89H
Intelligent Identifier (Device)
4
V
IH
V
IL
V
IL
V
IH
V
ID
V
IH
X
7CH
Write
5,6,7
V
IH
V
IL
V
IH
V
IL
X
X
V
PPH
D
IN
NOTES:
1. Refer to DC Characteristics.
2. X can be V
IL
, V
IH
for control pins and addresses, V
PPLK
or V
PPH
for V
PP
.
3. See DC Characteristics for V
PPLK
, V
PPH
, V
HH
, V
ID
voltages.
4. Manufacturer and device codes may also be accessed via a CUI write sequence, A
1
-A
17
= X.
5. Refer to Table 3 for valid D
IN
during a write operation.
6. Command writes for program or block erase are only executed when V
PP
= V
PPH
.
7. To write or erase the boot block, hold RP# at V
HH
.
8. RP# must be at GND
±
0.2V to meet the maximum deep power-down current specified.