VE28F008
Table 2. Bus Operations
Mode Notes RP CE OE WE A0V
PP
DQ
0–7
RY/BY
Read 1, 2, 3 V
IH
V
IL
V
ILVIH
XXD
OUT
X
Output Disable 3 V
IH
V
ILVIHVIH
X X High Z X
Standby 3 V
IH
V
IH
X X X X High Z X
PowerDown V
IL
X X X X X High Z V
OH
Intelligent Identifier (Mfr) V
IH
V
ILVIL
V
IH
V
IL
X 89H V
OH
Intelligent Identifier (Device) V
IH
V
ILVIL
V
IH
V
IH
X A2H V
OH
Write 3, 4, 5 V
IH
V
ILVIHVIL
XX DINX
NOTES:
1. Refer to DC Characteristics. When V
PP
e
V
PPL
, memory contents can be read but not written or erased.
2. X can be V
IL
or VIHfor control pins and addresses, and V
PPL
or V
PPH
for VPP. See DC Characteristics for V
PPL
and V
PPH
voltages.
3. RY/BY
is VOLwhen the Write State Machine is executing internal block erase or byte write algorithms. It is VOHwhen the
WSM is not busy, in Erase Suspend mode or deep powerdown mode.
4. Command writes involving block erase or byte write are only successfully executed when V
PP
e
V
PPH
.
5. Refer to Table 3 for valid D
IN
during a write operation.
data at the outputs. Chip Enable (CE) is the device
selection control, and when active enables the selected memory device. Output Enable (OE
)isthe
data input/output (DQ
0
–DQ7) direction control, and
when active drives data from the selected memory
onto the I/O bus. RP
and WE must also be at VIH.
Figure 8 illustrates read bus cycle waveforms.
Output Disable
With OE at a logic-high level (VIH), the device outputs are disabled. Output pins (DQ
0
–DQ7) are
placed in a high-impedance state.
Standby
CE at a logic-high level (VIH) places the VE28F008
in standby mode. Standby operation disables much
of the VE28F008’s circuitry and substantially reduces device power consumption. The outputs (DQ
0
–
DQ
7
) are placed in a high-impedence state indepen-
dent of the status of OE
. If the VE28F008 is deselected during block erase or byte write, the device
will continue functioning and consuming normal active power until the operation completes.
Deep Power-Down
The VE28F008 offers a deep powerdown feature,
entered when RP
is at VIL. During read modes, RP at
a logic-low level (V
IL
) deselects the memory, places
output drivers in a high-impedence state and turns
off all internal circuits. The VE28F008 requires time
t
PHQV
(see AC Characteristics-Read-Only Operations) after return from powerdown until initial memory access outputs are valid. After this wakeup interval, normal operation is restored. The Command
User Interface is reset to Read Array mode, and the
upper 5 bits of the Status Register are cleared to
value 10000, upon return to normal operation.
During block erase or byte write modes, RP
at a log-
ic-low level (V
IL
) will abort either operation. Memory
contents of the block being altered are no longer
valid as the data will be partially written or erased.
Time t
PHWL
after RP goes to logic-high (VIH) is re-
quired before another command can be written.
Intelligent Identifier Operation
The intelligent identifier operation outputs the manufacturer code, 89H; and the device code, A2H for
the VE28F008. The system CPU can then automatically match the device with its proper block erase
and byte write algorithms.
The manufacturer and device codes are read via the
Command User Interface. Following a write of 90H
to the Command User Interface, a read from address location 00000H outputs the manufacturer
code (89H). A read from address location 00001H
outputs the device code (A2H). It is not necessary to
have high voltage applied to V
PP
to read the intelli-
gent identifier from the Command User Interface.
7