20-668-0024 Rabbit Semiconductor, 20-668-0024 Datasheet - Page 53

• 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

The Rabbit 2000 and 3000 had numerous instructions for reading and writing data to logical
addresses, but only limited support for reading and writing data to a physical memory
address. This has changed for the Rabbit 4000—a wide range of instructions has been pro-
vided to read and write to physical addresses. It is possible to use the same instructions to
write to logical addresses as well.
The 64KB logical memory space limitation can also be expanded by using the separate
instruction and data space mode. When this mode is enabled, address bit A16 is inverted
for all data accesses in the root and/or data segments, while address bit A19 is inverted for
all data accesses in the root and/or data segments before bank selection (physical device)
occurs. These two features allow both code and data to access separate 64KB logical
spaces instead of sharing a single space.
It is possible to protect memory in the Rabbit 4000 at three different levels: each of the
memory banks can be made read-only, physical memory can be write-protected in 64KB
blocks, and two of those 64KB blocks can be protected with a granularity of 4KB. A
Priority 3 interrupt will occur if a write is attempted in one of the protected 64KB or 4KB
blocks. In addition, it is possible to place limits around the code execution stack and gen-
erate an interrupt if a stack-related write occurs within 16 bytes of those limits.
5.1.1 Block Diagram
Chapter 5 Memory Management
43