user manual

Disk I/O Support
B-19
B
Default 177Bug Controller and Device Parameters
177Bug initializes the parameter tables for a default configuration
of controllers and devices (refer to Appendix C). If the system needs
to be configured differently than this default configuration (for
example, to use a 70MB Winchester drive where the default is a
40MB Winchester drive), then these tables must be changed.
There are three ways to change parameter table contents:
❏ Using BO or BH. When you invoke one of these commands,
the configuration area of the disk is read and the parameters
corresponding to that device are rewritten according to the
parameter information contained in the configuration area.
This is a temporary change. If a cold-start reset occurs, then
the default parameter information is written back into the
tables.
❏ Using the IOT. You can use this command to reconfigure the
parameter table manually for any controller and/or device
that is different from the default. This is also a temporary
change and is overwritten if a cold-start reset occurs.
❏ Obtain the source. You can then change the configuration
files and rebuild 177Bug using different defaults. Changes
made to the defaults are permanent until changed again.
Disk I/O Error Codes
177Bug returns an error code if an attempted disk operation is
unsuccessful.
Network I/O Support
The Network Boot Firmware provides the capability to boot the
CPU through the ROM debugger using a network (local Ethernet
interface) as the boot device.
The booting process executes in two distinct phases: