TC58FVT641 datasheet(12/53 Pages) TOSHIBA

12 / 53 page

TC58FVT641/B641FT/XB-70,-10

2001-09-06

12/53

BLOCK PROTECTION

Block Protection is a function for disabling writing and erasing specific blocks. Block protection can be carried

out in two ways: by supplying a high voltage (VID) to the device (see Block protection 1) or by supplying a high

voltage and a command sequence (see Block protection 2).

(1) Block protection 1

Specify a device block address and make the following signal settings A9 = OE = VID, A1 = VIH and CE

= A0 = A6 = VIL. Now when a pulse is input to WE for tPPLH, the device will start to write to the block

protection circuit. Block protection can be verified using the Verify Block Protect command. Inputting VIL

on OE sets the device to Verify Mode. 01H is output if the block is protected and 00H is output if the block

is unprotected. If block protection was unsuccessful, the operation must be repeated. Releasing VID from A9

and OE terminates this mode.

(2) Block protection 2

Applying VID to RESET and inputting the Block Protect 2 command also performs block protection. The

first cycle of the command sequence is the Set-up command. In the second cycle, the Block Protect command

is input, in which a block address and A1 = VIH and A0 = A6 = VIL are input. Now the device writes to the

block protection circuit. There is a wait of tPPLH until this write is completed; however, no intervention is

necessary during this time. In the third cycle the Verify Block Protect command is input. This command

verifies the write to the block protection circuit. Read is performed in the fourth cycle. If the protection

operation is complete, 01H is output. If a value other than 01H is output, block protection is not complete

and the Block Protect command must be input again. Removing the VID input from RESET exits this

mode.

Temporary Block Unprotection

The TC58FVT641/B641 has a temporary block unprotection feature which disables block protection for all

protected blocks. Unprotection is enabled by applying VID to the RESET pin. Now Write and Erase operations

can be performed on all blocks except the boot blocks which have been protected by the Boot Block Protect

operation. The device returns to its previous state when VID is removed from the RESET pin. That is,

previously protected blocks will be protected again.

Verify Block Protect

The Verify Block Protect command is used to ascertain whether a block is protected or unprotected.

Verification is performed either by inputting the Verify Block Protect command or by applying VID to the A9 pin,

as for ID Read Mode, and setting the block address = A0 = A6 = VIL and A1 = VIH. If the block is protected, 01H

is output. If the block is unprotected, 00H is output.

Boot Block Protection

Boot block protection temporarily protects certain boot blocks using a method different from ordinary block

protection. Neither VID nor a command sequence is required. Protection is performed simply by inputting VIL

/ACC

. The target blocks are the two pairs of boot blocks. The top boot blocks are BA133 and BA134; the

bottom boot blocks are BA0 and BA1. Inputting VIH on

/ACC

releases the mode. From now on, if it is

necessary to protect these blocks, the ordinary Block Protection Mode must be used.

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