20-668-0024 Rabbit Semiconductor, 20-668-0024 Datasheet - Page 35

• 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

3. R
B
ESET AND
OOTSTRAP
3.1 Overview
The Rabbit 4000’s /RESET pin initializes everything in the processor except for the real-
time clock registers and the contents of the battery-backed onchip-encryption RAM. If a
write cycle is in progress, it waits until the write cycle is completed to avoid potential
memory corruption.
After reset, the Rabbit 4000 checks the state of the SMODE pins. Depending on their
state, it either begins normal operation by fetching instruction bytes from /CS0 and /OE0,
or it enters a special bootstrap mode where it fetches bytes from either Serial Port A or the
slave port. In this mode, bytes can be written to internal registers to set up the Rabbit 4000
for a particular configuration, or to memory to load a program. The processor can begin
normal operation once the bootstrap operation is completed.
3.1.1 Block Diagram
Chapter 3 Reset and Bootstrap
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