Motorola MVME166IG/D2 - Manual (Page 64)

Debugger General Information
3-18 MVME166 Single Board Computer Installation Guide
3
To perform a disk operation, 166Bug must eventually present a particular disk
controller module with a controller command packet which has been
especially prepared for that type of controller module. (This is accomplished
in the respective controller driver module.) A command packet for one type
of controller module usually does not have the same format as a command
packet for a different type of module. The system call facilities which do disk
I/O accept a generalized (controller-independent) packet format as an
argument, and translate it into a controller-specific packet, which is then sent
to the specified device. Refer to the system call descriptions in the Debugging
Package for Motorola 68K CISC CPUs User’s Manual for details on the format and
construction of these standardized "user" packets.
The packets which a controller module expects to be given vary from
controller to controller. The disk driver module for the particular hardware
module (board) must take the standardized packet given to a trap function
and create a new packet which is specifically tailored for the disk drive
controller it is sent to. Refer to documentation on the particular controller
module for the format of its packets, and for using the IOC command.
Default 166Bug Controller and Device Parameters
166Bug 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:
❏
Use 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.
❏ Use 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
166Bug so that it has different defaults. Changes made to the defaults are
permanent until changed again.