M28W640 STMicroelectronics, M28W640 Datasheet - Page 16

• Manufacturer Part Number: M28W640
• Description: 64 Mbit 4Mb x16/ Boot Block 3V Supply Flash Memory
• Manufacturer: STMicroelectronics

M28W640CT, M28W640CB
Table 7. Program, Erase Times and Program/Erase Endurance Cycles
Note: 1. Typical time to program a Main or Parameter Block using the Double Word Program and the Quadruple Word Program commands
BLOCK LOCKING
The M28W640C features an instant, individual
block locking scheme that allows any block to be
locked or unlocked with no latency. This locking
scheme has three levels of protection.
The protection status of each block can be set to
Locked, Unlocked, and Lock-Down. Table 9, de-
fines all of the possible protection states (WP,
DQ1, DQ0), and Appendix C, Figure 23, shows a
flowchart for the locking operations.
Reading a Block’s Lock Status
The lock status of every block can be read in the
Read Electronic Signature mode of the device. To
enter this mode write 90h to the device. Subse-
quent reads at the address specified in Table 5,
will output the protection status of that block. The
lock status is represented by DQ0 and DQ1. DQ0
indicates the Block Lock/Unlock status and is set
by the Lock command and cleared by the Unlock
16/54
Word Program
Double Word Program
Quadruple Word Program
Main Block Program
Parameter Block Program
Main Block Erase
Parameter Block Erase
Program/Erase Cycles (per Block)
Lock/Unlock - this first level allows software-
only control of block locking.
Lock-Down - this second level requires
hardware interaction before locking can be
changed.
V
hardware protection against program and erase
on all blocks.
PP
respectively.
V
PPLK
Parameter
- the third level offers a complete
Test Conditions
V
V
V
V
V
V
PP
PP
PP
PP
PP
PP
V
V
V
V
V
PP
PP
PP
PP
PP
= 12V ±5%
= 12V ±5%
= 12V ±5%
= 12V ±5%
= 12V ±5%
= 12V ±5%
= V
= V
= V
= V
= V
DD
DD
DD
DD
DD
command. It is also automatically set when enter-
ing Lock-Down. DQ1 indicates the Lock-Down sta-
tus and is set by the Lock-Down command. It
cannot be cleared by software, only by a hardware
reset or power-down.
The following sections explain the operation of the
locking system.
Locked State
The default status of all blocks on power-up or af-
ter a hardware reset is Locked (states (0,0,1) or
(1,0,1)). Locked blocks are fully protected from
any program or erase. Any program or erase oper-
ations attempted on a locked block will return an
error in the Status Register. The Status of a
Locked block can be changed to Unlocked or
Lock-Down using the appropriate software com-
mands. An Unlocked block can be Locked by issu-
ing the Lock command.
Unlocked State
Unlocked blocks (states (0,0,0), (1,0,0) (1,1,0)),
can be programmed or erased. All unlocked
blocks return to the Locked state after a hardware
reset or when the device is powered-down. The
status of an unlocked block can be changed to
Locked or Locked-Down using the appropriate
software commands. A locked block can be un-
locked by issuing the Unlock command.
100,000
Min
M28W640C
0.16/0.08
0.02/0.01
0.32
0.04
Typ
0.8
0.8
10
10
10
1
1
(1)
(1)
Max
200
200
200
10
10
10
10
5
4
5
4
cycles
Unit
µs
µs
µs
s
s
s
s
s
s
s
s