20-668-0003 Rabbit Semiconductor, 20-668-0003 Datasheet - Page 25

• Manufacturer Part Number: 20-668-0003
• Description: IC CPU RABBIT2000 30MHZ 100PQFP
• Manufacturer: Rabbit Semiconductor

Specifications of 20-668-0003

• Processor Type: Rabbit 2000 8-Bit
• Speed: 30MHz
• Voltage: 2.7V, 3V, 3.3V, 5V
• Mounting Type: Surface Mount
• Package / Case: 100-MQFP, 100-PQFP
• Data Bus Width: 8 bit
• Maximum Clock Frequency: 30 MHz
• Operating Supply Voltage: 0 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Number Of Programmable I/os: 40
• Number Of Timers: 8 & 10 bit
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Features: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 20-668-0003; 316-1062

than the XPC segment, can call other code in the root using short jumps and calls. Code in
the XPC segment can also call code in the root using short jumps and calls. However, a
long call must be used when code in the XPC segment is called. Functions located in the
root have an efficiency advantage because a long call and a long return require 32 clocks
to execute, but a short call and a short return require only 20 clocks to execute. The differ-
ence is small, but significant for short subroutines.
3.2.2 Extending Data Memory
In the normal memory model, the data space must share a 64K space with root code, the
stack, and the XPC window. Typically, this leaves a potential data space of 40K or less.
The XPC requires 8K, the stack requires 4K, and most systems will require at least 12K of
root code. This amount of data space is more than sufficient for most embedded applica-
tions.
One approach to getting more data space is to place data in RAM or in flash memory that
is not mapped into the 64K space, and then access this data using function calls or in
assembly language using the LDP instructions that can access memory using a 20-bit
address. This is satisfactory for accessing simple data structures or buffers.
Another approach to extending data memory is to use the stack segment to access data,
placing the stack in the data segment so as to free up the stack segment. This approach
works well for a software system that uses data groupings that are self-contained and are
accessed one at a time rather than randomly between all the groupings. An example would
Chapter 3 Details on Rabbit Microprocessor Features
10000
E000
D000
XPC segment
Stack segment
Data segment
Root segment
Figure 3-5. Use of XPC Segment
short
calls
returns
Compiler notices that
code has passed F000.
XPC=N
PC=F000+K
Illustration of sliding XPC window
Compiler inserts
long jump in code.
XPC=N+1
PC=E000+K+4
F000
E000
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