M29F032D データシートの表示（PDF） - STMicroelectronics
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M29F032D Datasheet PDF : 36 Pages
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M29F032D
BUS OPERATIONS
There are five standard bus operations that control
the device. These are Bus Read, Bus Write, Out-
put Disable, Standby and Automatic Standby. See
Tables 2, Bus Operations, for a summary. Typical-
ly glitches of less than 5ns on Chip Enable or Write
Enable are ignored by the memory and do not af-
fect bus operations.
Bus Read. Bus Read operations read from the
memory cells, or specific registers in the Com-
mand Interface. A valid Bus Read operation in-
volves setting the desired address on the Address
Inputs, applying a Low signal, VIL, to Chip Enable
and Output Enable and keeping Write Enable
High, VIH. The Data Inputs/Outputs will output the
value, see Figure 9, Read Mode AC Waveforms,
and Table 10, 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 desired address on the Ad-
dress 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 Com-
mand Interface on the rising edge of Chip Enable
or Write Enable, whichever occurs first. Output En-
able must remain High, VIH, during the whole Bus
Write operation. See Figures 10 and 11, Write AC
Waveforms, and Tables 11 and 12, Write AC
Characteristics, for details of the timing require-
ments.
Output Disable. The Data Inputs/Outputs are in
the high impedance state when Output Enable is
High, VIH.
Standby. When Chip Enable is High, VIH, the
memory enters Standby mode and the Data In-
puts/Outputs pins are placed in the high-imped-
ance state. To reduce the Supply Current to the
Standby Supply Current, ICC2, Chip Enable should
be held within VCC ± 0.2V. For the Standby current
level see Table 9, DC Characteristics.
During program or erase operations the memory
will continue to use the Program/Erase Supply
Current, ICC3, for Program or Erase operations un-
til the operation completes.
Automatic Standby. If CMOS levels (VCC ± 0.2V)
are used to drive the bus and the bus is inactive for
300ns or more the memory enters Automatic
Standby where the internal Supply Current is re-
duced to the Standby Supply Current, ICC2. 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 Protection. These bus opera-
tions are intended for use by programming equip-
ment and are not usually used in applications.
They require VID 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 the signals
listed in Tables 2, Bus Operations.
Block Protection and Blocks Unprotection.
Blocks can be protected in groups of 4 against ac-
cidental Program or Erase. See Appendix A, Table
16, Block Addresses, for details of which blocks
must be protected together as a group. 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 pro-
gramming equipment and the other for in-system
use. Block Protect and Chip Unprotect operations
are described in Appendix C.
Table 2. Bus Operations
Operation
E
G
W
Address Inputs
A0-A21
Data Inputs/Outputs
DQ7-DQ0
Bus Read
VIL
VIL
VIH Cell Address
Data Output
Bus Write
VIL
VIH
VIL Command Address
Data Input
Output Disable
X
VIH
VIH X
Hi-Z
Standby
VIH
X
XX
Hi-Z
Read Manufacturer
Code
VIL
VIL
VIH
A0 = VIL, A1 = VIL, A9 = VID, Others
VIL or VIH
20h
Read Device Code
VIL
VIL
VIH
A0 = VIH, A1 = VIL,
A9 = VID, Others VIL or VIH
Note: X = VIL or VIH.
ACh
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