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Chapter 3 Reset and Bootstrap
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3.2 Dependencies
3.2.1 I/O Pins
SMODE0, SMODE1 — When the Rabbit 5000 is first powered up or when it is reset, the
state of the SMODE0 and SMODE1 pins controls its operation.
SYSCFG0 — When the Rabbit 5000 is first powered up or when it is reset, the state of
this pin controls whether memory bank zero is mapped to /CS0 or the internal SRAM
(/CS3).
SYSCFG1 — This pin should always be tied to ground.
/RESET — Pulling the /RESET pin low will initialize everything in the Rabbit 5000
except for the real-time clock registers and the onchip-encryption RAM.
/CS1 — During reset the impedance of the /CS1 pin is high, and all other memory and I/O
control signals are held high. The special behavior of /CS1 allows an external RAM to be
powered by the same source as the VBATIO pin (which powers /CS1). In this case, a pul-
lup resistor is required on /CS1 to keep the RAM deselected during powerdown.
RESOUT — The RESOUT pin, which is powered by the backup battery, is high during
reset and powerdown as long as VBAT and VBATIO are present, but low at all other
times, and can be used to control an external power switch to disconnect VDDIO from
VBATIO when the main power source is removed.
3.2.2 Clocks
The processor requires a 32 kHz clock input to generate the 2400 bps internal clock
required for asynchronous serial bootstrap, which is used when booting via Dynamic C
and the Rabbit Field Utility. No 32 kHz clock is required for either clocked serial or slave
port bootstrap.
When the processor comes out of reset, the CPU clock and peripheral clocks are both in
divide-by-8 mode.
3.2.3 Other Registers
3.2.4 Interrupts
There are no interrupts associated with reset or bootstrap.
Register
Function
SPCR
Enable/disable processor monitoring of SMODE
pins; read current state of SMODE pins.
Содержание Rabbit 5000
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