Chapter 7. Public Key Execution Unit
7-31
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Miscellaneous Routines
7.5 Miscellaneous Routines
The remaining routines are general in nature and are not specific to any particular
cryptographic algorithm.
7.5.1 Clear Memory
This routine clears all of the RAM memory locations in the PKEU. This includes the A, B,
and N RAMs. All locations are set to zero. All other registers are cleared either via a reset
(software or hardware) or by explicitly writing zeros to each register. Following a reset
(software or hardware), this routine is automatically invoked. This accounts for the majority
of time between reset and the assertion of the DONE bit in the status register.
Figure 7-22. Clear Memory Register Usage
Table 7-23. Clear Memory
Clear Memory
Computation
A, B, N, and t memories are overwritten with zeros
Entry name
clearmemory
Entry address
0x00d(r2)
Pre-conditions
—
Post-conditions
A = B = N = 0 (all locations)
Unless explicitly noted, all other registers are not guaranteed to be any particular value.
Special
conditions
—
N1
N2
N3
A0
A1
A2
A3
B0
B1
B2
B3
Initial Condition
Final Condition
N0
0
0
XYZ
F2M
same
same
EXP(k)
regAsel
regBsel
regNsel
same
same
same
same
Modsize
EXP(k)_SIZE
same
same
0
0
0
0
0
0
0
0
0
0
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