SST38VF6401 Datasheet, PDF (20/64 Pages) Microchip Technology – 64 Mbit (x16) Advanced Multi-Purpose Flash Plus

64 Mbit (x16) Advanced Multi-Purpose Flash Plus
SST38VF6401 / SST38VF6402 / SST38VF6403 / SST38VF6404
Advanced Protection
Not Recommended for New Designs
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 Com-
mands 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 submitted, the
device takes approximately 2 µs to verify the password. A subsequent Submit Password command
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.
© 2015
DS-20005015B
08/15
20