668-0003-C Rabbit Semiconductor, 668-0003-C Datasheet - Page 172

• 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

16.1.2 BIOS Assumptions
The BIOS makes certain assumptions concerning the physical configuration of the proces-
sor. Processors are expected to have RAM connected to /CS1, /WE1, and /OE1. Flash is
expected to be connected to /CS0, /WE0, and /OE0. (See the Rabbit 2000 Designer’s
Handbook Memory Planning chapter if you want to design a board with RAM only.) The
crystal frequency is expected to be n*1.8432 MHz.
The Rabbit 2000 Designer’s Handbook has a chapter on the Rabbit BIOS with more
details.
16.2 Virtual Driver
The Virtual Driver is compiled with the user’s application. It includes support for the fol-
lowing services.
• Hitting the hardware watchdog timer.
• Decrementing software watchdog timers.
• Synchronizing the system timer variables with the real-time clock and keeping them
updated.
• Driving uC/OS-II multi-tasking.
• Driving slice statement multi-tasking.
16.2.1 Periodic Interrupt
The periodic interrupt that drives the Virtual Driver occurs every 16 clocks or every 488
µs. If the 32.768 kHz oscillator is absent, it is possible to substitute a different periodic
interrupt. This alternative is not supported by Rabbit Semiconductor since the cost of
connecting a crystal is very small. The periodic interrupt keeps the interrupts turned off
(that is, the processor priority is raised to 1 from zero) for about 75 clocks, so it contrib-
utes little to interrupt latency.
The periodic interrupt is turned on by default before
is called. It can be disabled if
main()
needed. The Dynamic C Users’s Manual chapter on the Virtual Driver provides more
details on the periodic interrupt.
The Rabbit 2000 microprocessor requires the 32 kHz oscillator in order to boot via
Dynamic C, unless a custom loader and BIOS are used.
16.2.2 Watchdog Timer Support
A microprocessor system can crash for a variety of reasons. A software bug or an electri-
cal upset are common reasons. When the system crashes the program will typically settle
into an endless loop because parameters that govern looping behavior have been cor-
rupted. Typically, the stack becomes corrupted and returns are made to random addresses.
The usual corrective action taken in response to a crash is to reset the microprocessor and
reboot the system. The crash can be detected either because an anomaly is detected by pro-
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Rabbit 2000 Microprocessor User’s Manual