20-668-0024 Rabbit Semiconductor, 20-668-0024 Datasheet - Page 56

• 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

5.3 Operation
5.3.1 Memory Management Unit (MMU)
Code execution takes place in the 64KB logical memory space, which is divided into four
segments: root, data, stack, and extended (XMEM). The root segment is always mapped
starting at physical address 0x000000, but the other segments can be remapped to start at
any physical 4KB block boundary.
The data and stack segment mappings are set by writing to the appropriate register, as
shown in Table 5-1. The DATASEG and STACKSEG registers provide backwards
compatibility to the Rabbit 2000 and 3000 processors; these registers map directly to
DATASEGL and STACKSEGL but the corresponding uppermost four bits are set to zero.
Each of these registers provides a 4KB offset that is added to the logical address to pro-
vide a physical address as shown in Figure 5-3.
46
DATASEG
DATASEGL
DATASEGH
STACKSEG
STACKSEGL
STACKSEGH
XPC
LXPC
Register
Table 5-1. Memory Management Registers
Segment
XMEM
XMEM
Stack
Stack
Stack
Data
Data
Data
12 bits
8 bits
8 bits
4 bits
8 bits
8 bits
4 bits
8 bits
Size
Maps to DATASEGL;
DATASEGH set to 0x00
Maps to STACKSEGL;
STACKSEGH set to 0x00
Loaded via instructions
LD XPC,A and LD A,XPC
Loaded via instructions:
LD LXPC,HL and LD HL,LXPC
Rabbit 4000 Microprocessor User’s Manual
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