668-0011 Rabbit Semiconductor, 668-0011 Datasheet - Page 57

• Manufacturer Part Number: 668-0011
• Description: IC MPU RABIT3000A 55.5MHZ128LQFP
• Manufacturer: Rabbit Semiconductor

Specifications of 668-0011

• Rohs Status: RoHS non-compliant
• Processor Type: Rabbit 3000 8-Bit
• Speed: 55.5MHz
• Voltage: 2.5V, 2.7V, 3V, 3.3V
• Mounting Type: Surface Mount
• Package / Case: 128-LQFP
• Features: -
• Other names: 316-1043

5.3.5 Stack Protection (Rabbit 3000A)
The ability to detect stack overflow and underflow was added starting with the Rabbit
3000A. Low and high stack limits can be set on 256-byte boundaries. When a stack-
relative memory access occurs within 16 bytes of these limits (or outside of them), a new
Priority 3 stack violation interrupt occurs. The 16-byte buffer exists to allow stack protec-
tion even if the stack is placed against a memory segment boundary.
Figure 5-6 shows one possible stack layout. A 2048-byte stack is set up by setting
STKHLR to 0x00E0, STKLLR to 0x00D8, and SP to 0xDFF0. Any stack-relative mem-
ory accesses above 0xDFEF (i.e., stack underflow) or below 0xD810 (i.e., overflow)
would trigger the stack violation interrupt.
Figure 5-6. Simple Stack Protection Layout
5.3.6 RAM Segment Relocation (Rabbit 3000A)
Normally when instruction/data separation is enabled, instructions are stored in flash
memory and data are stored in RAM memory. This can present a problem for the Interrupt
Service Routine area, which often requires run-time modification. The RAM Segment
Register (RAMSR) allows a 1, 2, or 4 KB segment of the logical memory space to be
mapped as data would be mapped, even for program execution.
Chapter 5 Memory Management
47