Datasheet

64 Mbit Multi-Purpose Flash Plus

SST39VF6401B / SST39VF6402B

Not Recommended for New Designs

Microchip Technology Company

Security ID

The SST39VF640xB devices offer a 256-bit Security ID space. The Secure ID space is divided into two

128-bit segments - one factory programmed segment and one user programmed segment. The first

segment is programmed and locked at SST with a random 128-bit number. The user segment is left

un-programmed for the customer to program as desired.

To program the user segment of the Security ID, the user must use the Security ID Word-Program

command. To detect end-of-write for the SEC ID, read the toggle bits. Do not use Data# Polling. Once

this is complete, the Sec ID should be locked using the User Sec ID Program Lock-Out. This disables

any future corruption of this space. Note that regardless of whether or not the Sec ID is locked, neither

Sec ID segment can be erased.

The Secure ID space can be queried by executing a three-byte command sequence with Enter Sec ID

command (88H) at address 555H in the last byte sequence. To exit this mode, the Exit Sec ID com-

mand should be executed. Refer to Table 6 for more details.