668-0003-C Rabbit Semiconductor, 668-0003-C Datasheet - Page 98

• 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

The memory management unit accepts a 16-bit address from the processor and translates
it into a 20-bit address. The procedure to do this works as follows.
1. It is determined which segment the 16-bit address belongs to by inspecting the upper 4
2. Each segment has an 8-bit segment register. The 8-bit segment register is added to the
92
SEGSIZE = 0x13
XPC
STACKSEG = 0x11
DATASEG = 0x12
bits of the address. Every address must belong to one of the possible 4 segments.
upper 4 bits of the 16-bit address to create a 20-bit address. Wraparound occurs if the
addition would result in an address that does not fit in 20 bits.
Segment Register
STACKSEG
DATASEG
XPC
+
Boundary SEGSIZE[4..7]
Boundary SEGSIZE[0..3]
00
20-bit address
16-bit address
Table 8-2. Segment Size Register
Table 8-1. Segment Registers
Figure 8-2. Memory Segments
Boundary address stack segment.
Locates extended code segment in physical memory. Read and written
by processor instructions: ld a,xpc, ld xpc,a, lcall, lret, ljp
Locates stack segment in physical memory.
Locates data segment in physical memory.
0K
64K
Bits 7..4
Rabbit 2000 Microprocessor User’s Manual
Function
Boundary address data segment.
Extended code
XPC segment (8K)
Stack segment
(4K typ)
Data segment
Root segment
Bits 3..0