SST38VF6402 datasheet(20/66 Pages) MICROCHIP

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DS20005015D

64 Mbit (x16) Advanced Multi-Purpose Flash Plus

SST38VF6401 / SST38VF6402 / SST38VF6403 / SST38VF6404

Advanced Protection

The SST38VF6401/6402/6403/6404 provide Advanced Protection features that allow users to imple-

ment conditional access to the NVPBs. Specifically, Advanced Protection uses the Global Lock Bit to

protect the NVPBs. If the Global Lock bit is ‘0’ then all the NVPBs states are frozen and cannot be

modified in any mode. If the Global Lock bit is ‘1’, then all the NVPBs can be modified in Non-Volatile

Block Protection mode. After using the Global Lock of NVPBs Entry command to enter the Global Lock

of NVPBs mode, the Global Lock Bit can be activated by issuing a Set Global Lock Bit command,

which sets the Global Lock Bit to ‘0’. The Global Lock bit cannot be set to ‘1’ with this command. The

status of the bit can be read with the Global Lock Bit Status command. Use the Global Lock of NVPBs

Exit command to exit Global Lock of NVPBs mode. See Table 11 and Figure 33 for further details.

The steps used to change the Global Lock Bit from '0' to'1,' to allow access to the NVPBs, depend on

whether the device has been set to use Pass-Through or Password mode. When using Advanced Pro-

tection, select either Pass-Through only mode or Password only mode by programming the DQ2 and

DQ1 bits in the PSR. Although the factory default is Pass-Through mode (DQ2 = 1, DQ1 = 1), the user

should explicitly chose either Pass-Through only mode (DQ2 = 1, DQ1 = 0), or Password only mode

(DQ2 = 0, DQ1 = 1). Keeping the SST38VF6401/6402/6403/6404 in the factory default Pass-Through

mode leaves the device open to unauthorized changes of DQ2 and DQ1 in the PSR. See “Protection

Settings Register (PSR)” on page 18. for more information about the PSR.

Pass-Through Mode (DQ2, DQ1 = 1,0)

The Pass-Through Mode allows the Global Lock Bit state to be cleared to ‘1’ by a power-down power-

up sequence or a hardware reset (RST# pin = 0). No password is required in Pass-Through mode.

To set the Global Lock Bit to ‘0’, use the Set Global Lock Bit command while in the Global Lock of

NVPBs mode. Select the Pass-Through only mode by programming PSR bit DQ2 = 1 and DQ1 = 0.

Password Mode (DQ2, DQ1 = 0,1)

In the Password Mode, the Global Lock Bit is set to ‘0’ by the Set Global Lock Bit command, a power-

down power-up sequence, or a hardware reset (RST# pin = 0). Select the Password only mode by pro-

gramming PSR bit DQ2 = 0 and DQ1 = 1. Note that when the PSR Program command is issued in

Password mode, the Global Lock bit is automatically set to ‘0’.

In contrast to the Pass-Through Mode, in the Password mode, the only way to clear the Global Lock

Bit to ‘1’ is to submit the correct 64-bit password using the Submit Password command in Password

Commands Mode. The words of the password can be submitted in any order as long as each 16 bit

section of the password is matched with its correct address. After the entire 64 bit password is submit-

ted, the device takes approximately 2 µs to verify the password. A subsequent Submit Password com-

mand cannot be issued until this verification time has elapsed.

The 64-bit password must be chosen by the user before programming the DQ2 and DQ1 OTP bits of

the PSR to choose Password Mode. The default 64 bit password on the device from the factory is

FFFFFFFFFFFFFFFFh.

Enter the Password Commands mode by issuing the Password Commands Entry command. Then,

use the Password Program command to program the desired password. Use caution when program-

ming the password because there is no method to reset the password to FFFFFFFFFFFFFFFFh.

Once a password bit has been set to ‘0’, it cannot be changed back to ‘1’. See Table 11 for further

details about Password-related commands.

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