SST38VF6402 datasheet(19/64 Pages) MICROCHIP

19 / 64 page

DS-20005015B

08/15

64 Mbit (x16) Advanced Multi-Purpose Flash Plus

SST38VF6401 / SST38VF6402 / SST38VF6403 / SST38VF6404

Not Recommended for New Designs

Individual Block Protection

The SST38VF6401/6402/6403/6404 provide two methods for Individual Block protection: Volatile Block

Protection and Non-Volatile Block Protection. Data in protected blocks cannot be altered.

Volatile Block Protection

The Volatile Block Protection feature provides a faster method than Non-Volatile Protection to protect

and unprotect 32 KWord blocks. Each block has it’s own Volatile Protection Bit (VPB). In the

SST38VF6401/2, the 32 KWord boot block also has a VPB. In the SST38VF6403/4 devices, each of

the two 4 KWord sectors in the 8 KWord boot area has it's own VPB.

After using the Volatile Block Protection Mode Entry command to enter the Volatile Block Protection

mode, individual VPBs can be set or reset with VPB Set/Clear, or be read with VPB Status Read. If the

VPB is ‘0’, then the block is protected from Program and Erase. If the VPB is ‘1’, then the block is

unprotected. The Volatile Block Protection Exit command must be issued to exit Volatile Block Protec-

tion mode. See Table 11 for further details on the commands and Figure 31 for a flow chart.

If the device experiences a hardware reset or a power cycle, all the VPBs return to their default state

as determined by user-programmable bit DQ4 in the PSR. If DQ4 is ‘0’, then all VPBs default to ‘0’ (pro-

tected). If DQ4 is ‘1’, then all VPBs default to ‘1’ (unprotected).

Non-Volatile Block Protection

The Non-Volatile Block Protection feature provides protection to individual blocks using Non-Volatile

Protection Bits (NVPBs). Each block has it’s own Non-Volatile Protection Bit. In the SST38VF6401/2,

the 32 KWord boot block also has a it's own NVPB. In the SST38VF6403/4, each 4 KWord sector in

the 8KWord boot area has it's own NVPB. All NVPBs come from the factory set to ‘1’, the unprotected

state.

Use the Non-Volatile Block Protection Mode Entry command to enter the Non-Volatile Block Protection

mode. Once in this mode, the NVPB Program command can be used to protect individual blocks by

setting individual NVPBs to ‘0’. The time needed to program an NVPB is two times TBP, which is a max-

imum of 20µs. The NVPB Status Read command can be used to check the protection state of an indi-

vidual NVPB.

To change an NVPB to ‘1’, the unprotected state, the NVPB must be erased using NVPBs Erase com-

mand. This command erases all NVPBs to ‘1’. NVPB Program should be used to set the NVPBs of any

blocks that are to be protected before exiting the Non-Volatile Block Protection mode. See Table 11

and Figure 32 for further details.

Upon a power cycle or hardware reset, the NVPBs retain their states. Memory areas that are protected

using Non-Volatile Block Protection remain protected. The NVPB Program and NVPBs Erase com-

mands are permanently disabled once the Irreversible Block Lock command is issued. See “Irrevers-

ible Block Locking” on page 22 for further information.

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