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Rabbit 6000 User’s Manual
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67
5.3.6 Memory Protection
Memory blocks may be protected at three separate granularities, as shown in Table 5-4. Writes can be pre-
vented to any memory bank by writing to MBxCR. Writes can be prevented and trapped at a resolution of
64 KB by enabling protection for that block in the appropriate WPxR register. For further control, two of
those 64 KB blocks can be further subdivided into 4 KB blocks by selecting them as the write protect seg-
ments A or B.
When a write is attempted to a block protected in WPxR, WPSxLR, or WPSxHR, a Priority 3 write-protect
interrupt occurs. This feature is automatically enabled by writing to the block protection registers; to dis-
able it, set all the write-protect block registers to zero.
5.3.7 Stack Protection
The Rabbit 6000 provides stack overflow and underflow protection. Low and high logical address limits
can be set in STKLLR and STKHLR; a Priority 3 stack-violation interrupt occurs when a stack-based
write occurs within the 16 bytes below the upper limit or within the 16 bytes above the lower limit. Note
that the writes will still occur even if they are within the 16 bytes surrounding the limits, but the interrupt
can serve as a warning to the application that the stack is in danger of being over or underrun.
The stack checking can be enabled or disabled by writing to STKCR.
Table 5-4. Memory Protection Options
Method
Block Size
Registers Used
Memory Bank
128 KB – 4 MB
MBxCR, MECR
Write-Protect Blocks
64 KB
WPxR
Write Protect Segment A/B
4 KB
WPSxR, WPSxLR, WPSxHR
Summary of Contents for 6000
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