Motorola MVME166D2, MVME166IG/D2 manual Default 166Bug Controller and Device Parameters

Debugger General Information

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

3of 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.

3-18 MVME166 Single Board Computer Installation Guide