m29w400db STMicroelectronics, m29w400db Datasheet - Page 16

• Manufacturer Part Number: m29w400db
• Description: 4 Mbit 512kb X8 Or 256kb X16, Boot Block 3v Supply Flash Memory
• Manufacturer: STMicroelectronics

Bus operations
3
3.1
3.2
3.3
3.4
3.5
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Bus operations
There are five standard bus operations that control the device. These are Bus Read, Bus
Write, Output Disable, Standby and Automatic Standby. See
operations, for a summary. Typically glitches of less than 5 ns on Chip Enable or Write
Enable are ignored by the memory and do not affect bus operations.
Bus Read
Bus Read operations read from the memory cells, or specific registers in the command
interface. A valid Bus Read operation involves setting the desired address on the Address
inputs, applying a Low signal, V
Enable High, V
AC
becomes valid.
Bus Write
Bus Write operations write to the command interface. A valid Bus Write operation begins by
setting the desired address on the Address inputs. The Address inputs are latched by the
command interface on the falling edge of Chip Enable or Write Enable, whichever occurs
last. The Data inputs/outputs are latched by the command interface on the rising edge of
Chip Enable or Write Enable, whichever occurs first. Output Enable must remain High, V
during the whole Bus Write operation. See
and
Output Disable
The Data inputs/outputs are in the high impedance state when Output Enable is High, V
Standby
When Chip Enable is High, V
inputs/outputs pins are placed in the high-impedance state. To reduce the Supply current to
the Standby Supply current, I
Standby current level see
During program or erase operations the memory will continue to use the Program/Erase
Supply current, I
Automatic Standby
If CMOS levels (V
more the memory enters Automatic Standby where the internal Supply current is reduced to
the Standby Supply current, I
operation is in progress.
waveforms, and
Table 13
and
IH
CC3
. The Data inputs/outputs will output the value, see
Table
CC
Table 12: Read AC
, for Program or Erase operations until the operation completes.
± 0.2 V) are used to drive the bus and the bus is inactive for 150 ns or
14, Write AC characteristics, for details of the timing requirements.
Table 11: DC
CC2
IH
CC2
, the memory enters Standby mode and the Data
IL
. The Data inputs/outputs will still output data if a Bus Read
, Chip Enable should be held within V
, to Chip Enable and Output Enable and keeping Write
characteristics, for details of when the output
characteristics.
Figure 12
and
Figure
Table 2
M29W400DT, M29W400DB
13, Write AC waveforms,
Figure 11: Read mode
and
CC
Table
± 0.2 V. For the
3, Bus
IH
IH
.
,