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M29W004BT, M29W004BB
Table 5. Bus Operations
Note: X = VIL or VIH.
Operation E G W Address Inputs
Data
Inputs/Outp uts
Bus Read
V
IL
V
IL
V
IH
Cell Address Data Output
Bus Write
V
IL
V
IH
V
IL
Command Address Data Input
Output Disable
XV
IH
V
IH
X Hi-Z
Standby
V
IH
X X X Hi-Z
Read Manufacturer
Code
V
IL
V
IL
V
IH
A0 = VIL, A1 = VIL, A9 = VID,
Others V
IL
or V
IH
20h
Read Device Code
V
IL
V
IL
V
IH
A0 = VIH, A1 = VIL, A9 = VID,
Others V
IL
or V
IH
EAh (M29W004BT)
EBh (M29W004BB)
BUS OPERATIONS
There are five standard bus operations that control
the device. These are Bus Read, Bus Wri te, Output Disable, Standby and Automatic Standby. See
Table 5, Bus Operations, for a summary. Typically
glitches of less than 5ns on Chip Enabl e o r Write
Enable are ignored by t he mem ory and do not a ffect 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 sig nal, V
IL
, to Chip Enable
and Output Enable and keeping Write Enable
High, V
IH
. The Data Inputs/Outputs will output the
value, see Figure 7, Rea d Mode AC Wav eforms,
and Table 12, Read AC Characteristics, for details
of when the output becomes valid.
Bus Write. Bus Write operations write to the
Command Interface. A valid Bus Write operation
begins by setting the desire d address on t he 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 a re latched by the Command Interface on the rising edge of Chip Enable
or Write Enable, whichever occurs first. Output Enable must remain High, V
IH
, during the whole Bus
Write operation. See Figures 8 and 9, Write AC
Waveforms, and Tables 13 and 14, Write AC
Characteristics, for details of the timing requirements.
Output Disa bl e . The Data Inputs/Outputs are in
the high impedance s tate when Output Enable is
High, V
IH
.
Standby. When Chip Enable is High, V
IH
, the
memory enters Standby mode and the Data Inputs/Outputs pins are placed in the high-imped-
ance state. To reduce the S upply Current to the
Standby Supply Current, I
CC2
, Chip Enable should
be held within V
CC
± 0.2V. For the Standby current
level see Table 11, DC Characteristics.
During program or erase operations the memory
will continue to use the Program/Erase Supply
Current, I
CC3
, for Program or Erase operations un-
til the operation completes.
Automatic Standby. If CMOS levels (V
CC
± 0.2V)
are used to drive the bus and the bus is inactive for
150ns or more the memory enters Automatic
Standby where the internal Supply Current is reduced to the Standby Supply Current, I
CC2
. The
Data Inputs/Outputs will still output data if a Bus
Read operation is in progress.
Special Bus Operations
Additional bus operations can be performed to
read the Electronic Signature and also to apply
and remove Block Protec tion. These bus operations are intended for use by programming equipment and are not usually used in applications.
They require V
ID
to be applied to some pins.
Electronic Signature. The memory has two
codes, the manufacturer code and the device
code, that can be read to identify the memory.
These codes can be read by applying t he signals
listed in Table 5, Bus Operations.
Block Protectio n and Blocks Unprotection. Each
block can be separately protected against accidental Program or Erase. Protected blocks can be
unprotected to allow data to be changed.
There are two methods available for protecting
and unprotecting the blocks, one for use on programming equipment and the other for in-system
use. For further information refer to Application
Note AN1122, Applying P rotection and Unp rotection to M29 Series Flash.