BBC MICRO RESOURCE SHARING AND IMPLEMENTATION OF VIRTUAL MEMORY ON MEX68KECB

Abstract

The Motorola MC68000 Educational Computer Board (MEX68KECB) is Interfaced with BBC Microcomputer, in both the serial and parallel modes of data transfer. BBC auxiliary. storage is shared between the two systems which enables the user of MEX68KECB with an efficient back up storage. The programs of MEX68KECB can be saved to, loaded and deleted from floppy with the help of simple commands. The virtual memory is implemented by using the segmented memory manage-ment with the assumption that all the segments are reloca-table and no segment modifies other segment. First In First Out (FIFO) algorithm is used for removing the segments from the memory and dynamic linking and loading is achieved with the help of the segment Map Table. The Directories are also implemented to keep the information of different users seperate in case they use the same floppy. A provision to connect the two directories and changing the password of a particular directory is made. Fifteen commands are defined in monitor mode to facilitate the user to get the services of the system and control the BBC from the terminal attached with MEX68KECB