Rev. 1.50, 10/04, page 199 of 448
9.4 L Memory Protective Functions
The SH-4A implements the following protective functions to the L memory by using the on-chip
memory access mode bit (RMD) and the on-chip memory protection enable bit (RP) in the on-chip
memory control register (RAMCR).
• Protective functions for access from the CPU and FPU
When RAMCR.RMD = 0, and the L memory is accessed in user mode, it is determined to be
an address error exception.
When MMUCR.AT = 1 and RAMCR.RP = 1, MMU exception and address error exception are
checked in the L memory area which is a part of area P4 as with the area P0/P3/U0.
The above descriptions are summarized in table 9.4.
Table 9.4 Protective Function Exceptions to Access L Memory
MMUCR.AT RAMCR.RP SR.MD RAMCR. RMD
Always Occurring
Exceptions
Possibly Occurring
Exceptions
0 Address error
exception
—
0
1 — —
0 *
1 * — —
0 Address error
exception
— 0
1 — —
0
1 * — —
0 Address error
exception
— 0
1 — MMU exception
1
1
1 * — MMU exception
[Legend] *: Don't care
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