Block protection
M58LT256JST, M58LT256JSB
9
Block protection
The M58LT256JST/B features an instant, individual block protection scheme that allows any
block to be protected or unprotected with no latency. This protection scheme has two levels
of protection.
●
●
Protect/unprotect - this first level allows software only control of block protection.
V
PP
≤
V
PPLK
- this second level offers a complete hardware protection against program
and erase on all blocks.
The protection status of each block can be set to protected and unprotected.
shows a flowchart for the protection operations.
9.1
Reading a block’s protection status
The protection status of every block can be read in the read electronic signature mode of the
device. To enter this mode issue the Read Electronic Signature command. Subsequent
reads at the address specified in
output the protection status of that block.
The protection status is represented by DQ0. DQ0 indicates the block protect/unprotect
status, is set by the Protect command, and cleared by the Unprotect command.
The following sections explain the operation of the protection system.
9.2
Protected state
The default status of all blocks on power-up or after a hardware reset is protected (state =
1). Protected blocks are fully protected from program or erase operations. Any program or
erase operations attempted on a protected block return an error in the Status Register. The
status of a protected block can be changed to unprotected using the appropriate software
commands. An unprotected block can be protected by issuing the Protect command.
9.3
Unprotected state
Unprotected blocks (state = 0) can be programmed or erased. All unprotected blocks return
to the protected state after a hardware reset or when the device is powered-down. The
status of an unprotected block can be changed to protected using the appropriate software
commands. A protected block can be unprotected by issuing the Unprotect command.
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NUMONYX [ NUMONYX B.V ]
