Digi Rabbit 5000, User Manual

Page: 37 / 414

Chapter 3 Reset and Bootstrap 37
3. R
ESET AND
B
OOTSTRAP
3.1 Overview
The Rabbit 5000’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 5000 checks the state of the SMODE and SYSCFG pins. Depending
on the state of the SMODE pins, it either begins normal operation by fetching instruction
bytes from memory bank zero, which is mapped to either /CS0 or /CS3 depending on the
state of the SYSCFG0 pin, 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 5000 for a particular configuration, or to memory to load a
program. The processor can begin normal operation once the bootstrap operation is
completed.