TCC720 Datasheet, PDF (138/143 Pages) List of Unclassifed Manufacturers – 32-bit RISC Microprocessor For Digital Media Player

TCC720
32-bit RISC Microprocessor for Digital Media Player
Dec. 16. 2002
BOOTING PROCEDURE
Preliminary Spec 0.51
14.4 NOR Boot with Security
There are two modes for booting from NOR flash. One is booting from external ROM that is
commonly used for various applications, and the other is booting from encrypted external ROM
that can be used to hide one’s code from the non-authorized user.
It can be selected by setting GPIO_A[10:8] appropriately as described in table 14.1.
In both cases, the NOR flash must be connected via nCS3 signal.
In case of non-encrypted mode, the F/W code in external flash is directly fetched to TCC720
without any other intermediate processing, but in case of encrypted mode, the F/W code in
external flash is stored in encrypted value, so boot ROM must decrypt it ahead and then copy
these codes to the other random accessible memories.
Figures 14.5 illustrate the allocation map of encrypted F/W code in NOR flash.
1 byte
0x00000000
0x00000004
0x00000008
SA + 8
Size of Initialization Code (= S_A = S_A3*2²⁴ + S_A2*2¹⁶ + S_A1*2⁸ + S_A0)
S_A0
S_A1
S_A2
S_A3
Size of F/W Code (= S_B = S_B3*2²⁴ + S_B2*2¹⁶ + S_B1*2⁸ + S_B0)
S_B0
S_B1
S_B2
S_B3
Initialization Code Area (S_A bytes)
.
.
.
Returning from these area, the register R0 contains
the start address of F/W code
R0
Main F/W Code Area (S_B bytes)
Figure 14.5 Allocation of encrypted F/W code
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