668-0003-C Rabbit Semiconductor, 668-0003-C Datasheet - Page 26

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

Specifications of 668-0003-C

• Rohs Status: RoHS non-compliant
• 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
• Features: -
• Other names: 316-1004; 668-0003

be the software structures associated with a TCP/IP communication protocol connection
where the same code accesses the data structures associated with each connection in a pat-
tern determined by the traffic on each connection.
The advantage of this approach is that normal C data access techniques, such as 16-bit
pointers, may be used. The stack segment register has to be modified to bring the data
structure into view in the stack segment before operations are performed on a particular
data structure. Since the stack has to be moved into the data area, it is important that the
number of stacks required be kept to a minimum when using the stack segment to view
data. Of course, tasks that don’t need to see the data structures can have their stack located
in the stack segment. Another possibility is to have a data structure and a stack located
together in the stack segment, and to use a different stack segment for different tasks, each
task having its own data area and stack bound to it.
These approaches are shown in Figure 3-6 below.
A third approach is to place the data and root code in RAM in the root segment, freeing the
data segment to be a window to extended memory. This requires copying the root code to
RAM at startup time. Copying root code to RAM is not necessarily that burdensome since
the amount of RAM required can be quite small, say 12K for example.
20
Using Stack Segment
for a Data Window
(RAM)
(flash)
Root
Code
Data
Figure 3-6. Schemes for Data Memory Windows
Stack Seg-
ment used as
data window
Stacks in data
segment
Root Segment
mapped to
RAM has both
root code and
data.
Data Segment
used as data
window
Using Data Segment for
a Data Window (Code must
be copied to RAM on startup.)
Rabbit 2000 Microprocessor User’s Manual
(RAM)
(RAM)
Root
Code
Data
Stack Seg-
ment used for
stack