DS5002FP

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this action. In addition, power is momentarily removed from the byte-wide bus interface including the

TOP LAYER COATING

The DS5002FPM is provided with a special top-layer coating that is designed to prevent a probe attack.

This coating is implemented with second-layer metal added through special processing of the

microcontroller die. This additional layer is not a simple sheet of metal, but rather a complex layout that

is interwoven with power and ground, which are in turn connected to logic for the Encryption Key and

the Security Lock. As a result, any attempt to remove the layer or probe through it will result in the

erasure of the Security Lock and/or the loss of Encryption Key bits.

BOOTSTRAP LOADING

Initial loading of application software into the DS5002FP is performed by firmware within the on-chip

Bootstrap Loader communicating with a PC via the on-chip serial port in a manner which is almost

identical to that for the DS5001FP. The user should consult the DS5001FP data sheet as a basis of

operational characteristics of this firmware. Certain differences in loading procedure exist in order to

support the security feature.

These differences are documented below. Table 1 summarizes the

commands accepted by the bootstrap loader.

When the Bootstrap Loader is invoked, portions of the 128-byte scratchpad RAM area are automatically

overwritten with zeroes, and then used for variable storage for the bootstrap firmware. Also, a set of 8

bytes are generated using the random number generator circuitry and are saved as a potential word for the

64-bit Encryption Key.

Any read or write operation to the DS5002FP’s external program/data SRAM can only take place if the

Security Lock bit is in a cleared state. Therefore, the first step which is taken in the loading of a program

should be the clearing of the Security Lock bit through the “U” command.