Maxim Integrated Secure Microcontroller User Manual
Page 17
Secure Microcontroller User’s Guide
17 of 187
Vector RAM
The vector RAM is used to contain the reset and interrupt vector code when the soft microcontroller is
operating in the encryption mode. This feature is included to insure the security of the application
software. The operation of the vector RAM as well as the reason for its inclusion in the architecture are
discussed in Software Security in Section
Timed-Access Logic
The timed-access logic protects against inadvertent changes to configuration and to the program RAM in
the event of a loss of software control. The protected configuration parameters include the partition
address bits in the MCON register as well as the enable watchdog-timer bit, stop mode bit, and power-on
reset bit in the PCON register.
Watchdog Timer
When the user’s software is being executed, the watchdog timer can be used to automatically restart the
processor in the event that software control is lost. It is also used to generate an oscillator start-up delay to
allow the clock frequency to stabilize. This occurs during reset cycles that follow a time in which the
oscillator has been stopped (stop mode reset and power-on reset).
Resident Loader ROM
The resident loader ROM contains firmware that controls the initial loading of the nonvolatile
program/data RAM. The firmware provides serial bootstrap load operation via the on-chip serial port. The
internal ROM is not accessible by the user and performs the loading function only when the device is
strapped for operation in the program mode. The ROM becomes transparent to the user once loading is
complete and has no affect on the memory map.