Personal Computer User Manual

Disk I/O Support
MVME197LEIG/D1 3-13
3
Default 197Bug Controller and Device Parameters
197Bug initializes the parameter tables for a default configuration of
controllers and devices (refer to Appendix B). 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 the parameter tables:
❏ Using BO or BH. When the user invokes 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 IOT. The user can use this command to manually reconfigure the
parameter table 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. The user may change the configuration files and rebuild
197Bug so that it has different defaults. Changes made to the defaults are
permanent until changed again.
Disk I/O Error Codes
197Bug 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 is executed in two distinct phases.
❏ The first phase allows the diskless remote node to discover its network
identity and the name of the file to be booted.
❏ The second phase has the diskless remote node reading the boot file across
the network into its memory.
The various modules (capabilities) and the dependencies of these modules
that support the overall network boot function are described in the following
paragraphs.