Rockwell Automation 6182 SDK - Manual (Page 14)

1–8 Introduction to the RAC6182
Publication 6182-UM002B-EN-P
generator time to stabilize. Finally, system DRAM is tested. In the
interest of reducing boot time, this test is limited to an address check; no
attempt is made to identify bit errors at given addresses.
Tests for Boot Devices
When hardware testing has been completed, the boot code starts looking
for PCMCIA devices capable of supplying a compressed operating
system image.
The boot code first checks for the presence of a PCMCIA ATA memory
device. If it finds such a device with a FAT16 file system containing a
file recognizable by its name as a compressed boot image, it will attempt
to use that image. The image will be tested for validity. If valid it will
be used to overwrite any existing image on the Disk-On-Chip. Operating
system loading will then commence.
Note: The boot process configures the PCI controller and any
NE2000 Ethernet device in the PCI slot to the extent that,
after boot, applications will be able to obtain necessary
address and interrupt information by querying the device.
This basic POST setup does not necessarily configure all
configuration space registers such a device may use.
Though many PCI devices will not need any other
configuration space registers configured after boot, some
have special power-management or other registers to
configure. These registers vary widely by card and should
be setup by application after boot using Win API calls to
access PCI configuration space.
Load of Compressed Operating System
The boot code reads the compressed operating system image from the
Disk-On-Chip operating system partition, decompresses it and loads it
into memory. (It loads the executable operating system code into
program memory and a default system registry into the RAMDISK
section of memory.) Control then passes to the operating system image
in memory.
“Cold Boot”
The operating system begins a “cold boot” by loading the driver for the
FAT file system on the Disk-On-Chip.
It then attempts to find the primary persistent registry file. If this file is
not present, it attempts to find the backup persistent registry file. If no
persistent registry file is found, system boot continues with the default
registry already in memory.
If a persistent registry file is found, the system merges the default
operating system registry and this saved persistent registry, saved
persistent registry items taking precedence.