20-668-0024 Rabbit Semiconductor, 20-668-0024 Datasheet - Page 293

IC CPU RABBIT4000 128-LQFP

20-668-0024

Manufacturer Part Number
20-668-0024
Description
IC CPU RABBIT4000 128-LQFP
Manufacturer
Rabbit Semiconductor
Datasheet

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

Available stocks

Company
Part Number
Manufacturer
Quantity
Price
Part Number:
20-668-0024
Manufacturer:
Rabbit Semiconductor
Quantity:
10 000
27.1 Overview
The Rabbit 4000 provides support for two tiers of control in the processor: System Mode,
which provides full access to all processor resources; and User Mode, a more restricted
mode. Table 27-1 describes the essential differences between the System Mode and the
User Mode. The System Mode is essentially the same as the normal operation when the
System/User Mode is disabled.
The main intent of the System/User Mode is to protect critical code (for example, code
that performs remote firmware updates), data, and the current processor state (memory
setup, peripheral control, etc.) from inadvertent changes by the user’s standard code. By
removing access to the processor’s I/O registers and preventing memory writes to critical
regions, the user’s code can run without the danger of locking up the processor to the point
where it cannot be restarted remotely and/or new code uploaded.
Chapter 27 System/User Mode
All peripherals accessible.
All processor control registers available.
All interrupt priorities available.
IDET instruction has no effect.
No write protection when 0x00 is written to
WPCR (write protection in User mode only)
Easy to enter user mode (SETUSR instruction).
Table 27-1. Differences Between System Mode and User Mode
System Mode
27. S
No peripherals accessible by default.
No processor control registers available.
Interrupt Priority 3 not allowed.
IDET instruction causes Priority 3 “System
mode violation” interrupt.
Write to protected segment causes Priority 3
“write protection violation” interrupt.
Difficult to enter system mode (requires
interrupt, SYSCALL, or RST instruction).
YSTEM
User Mode
/U
SER
M
ODE
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