M58LT128HSB datasheet(49/110 Pages) STMICROELECTRONICS

49 / 110 page

M58LT128HST, M58LT128HSB

Block protection

49/110

Block protection

The M58LT128HST/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.

●

VPP ≤VPPLK - the 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. Appendix C,

Figure 25, 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 Table 7, will output the protection status of that block.

The protection status is represented by DQ0. DQ0 indicates the Block Protect/Unprotect

status and 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 will 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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