Bus Direction Add-On For Msx Extensions

52 The majority of MSX computers do not require a BUSDIR (bus direction) signal from add-on circuits plugged into slots. A problem arises, however, if the extension circuits published in Elektor Electronics are used in conjunction with, for example, a Sanyo MSX machine, which has a few peculiarities in its exter- nal I/O concept. In general, the more slots on an MSX com- puter, the higher the prob- ability that either one of, or both, these circuits are re- quired to be able to use the home-made extensions. Two solutions are offered to provide for the BUSDIR signal. BUS DIRECTION ADD-ON FOR MSX EXTENSIONS One is usable for the Universal I/O Bus and the I/O & Timer Cartridge, the other for the Car- tridge Busboard. Each of these circuits consists of one IC only. Circuit A is used with the two I/O extensions, and is readily incorporated in the computer, at a suitable location near the slot that receives the extension. If necessary, all slots on the computer are fitted with this cir-...