20-668-0024 Rabbit Semiconductor, 20-668-0024 Datasheet - Page 297

• Manufacturer Part Number: 20-668-0024
• Description: IC CPU RABBIT4000 128-LQFP
• Manufacturer: Rabbit Semiconductor

Specifications of 20-668-0024

• Processor Type: Rabbit 4000 8-bit
• Speed: 60MHz
• Voltage: 2.5V, 2.7V, 3V, 3.3V
• Mounting Type: Surface Mount
• Package / Case: 128-LQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Other names: 20-668-0022; 316-1078

27.3 Operation
The System/User Mode is designed to work with the memory and stack protection features
of the Rabbit 4000 processor to provide a seamless framework for protection of critical
code. However, there are many levels at which the System/User Mode can be used —
some examples are described here.
27.3.1 Memory Protection Only
At the beginning of the user program, all necessary peripherals are enabled, all peripheral
interrupts to be used are set up for the User Mode, critical memory regions are protected,
stack limits are set, and the various system/memory/stack violation interrupts are enabled.
The processor then enters the User Mode and remains in the User Mode for all operations
(interrupts can be handled however the user desires). Obviously the critical interrupts can
be handled in the System Mode, but at that point the device is typically reset and the error
is logged. Figure 27-1 shows an overview of this level of operation.
System Mode
User Mode
Application
Critical
code
interrupts
Critical
Interrupts
Interrupts
Figure 27-1. System/User Mode Setup for Memory Protection Only
Chapter 27 System/User Mode
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