The 3B20D Processor & DMERT Operating System: 3B20D Input/Output System
A. H. Budlong, F. W. Wendland · Bell System Technical Journal · 1983
The 3B20D Input/Output system supports a large number of peripheral devices of various types. The 3B20D Input/Output Processor was designed for maximum flexibility because of the diversity of the peripheral interface requirements. Because of this diversity the basic structure was developed around a high-speed bipolar multiplexor. This multiplexor interfaces with a standard microprocessor bus to numerous specialized one- or two-board computers, which interface to the peripheral devices. Power and unit designs of the input/output processor also provide flexibility in power control and ground isolation of the peripherals. The variety of peripheral units include slow- and medium-speed tape drives (including streamers), low- and high-speed data links, medium to very-high-speed printers, and scanner and signal distributor circuits.