Abstract: An apparatus for intersystem I/O channel paging. The I/O channel through an I/O channel adapter provides communication between a central processor, an I/O processor, and a shared electronic storage device. The central processor and I/O processor are each enabled for recognizing specific instructions. The intersystem channel may be implemented in the form of a page chain table. Either process is capable of constructing a page chain table in the shared electronic storage device, upon receipt of appropriate instructions. The central processor or I/O processor signals the I/O channel adapter with identification of a page chain table to select. The I/O channel adapter fetches table entries and executes the table. The I/O channel adapter initiates I/O activity upon execution of the table. The I/O channel is not dependent upon the central processor or I/O processor for fetching or executing instructions, rather it acts independent of the processors once the page chain table is created.

Abstract: A power-on reset circuit is used to initialize a system component upon power-on. The circuit comprises a digital circuit such as a shift register which exhibits a multiplicity of uncertain or random outputs upon power-on. These output are coupled to digital logic such as an AND gate which itself outputs a power-on reset signal when any of the outputs of the shift register is not a predetermined output level. Because the outputs of the shift register are uncertain or arbitrary upon power-on and there are a multiplicity of such outputs, it is not likely that all of the outputs of the shift register will coincidentally exhibit the predetermined levels upon power-on. Consequently, it is very likely that the AND gate will provide the power-on reset signal upon power-on to initialize the system component.

Abstract: A high performance channel-to-channel adapter for interconnecting two or more digital computers or digital data processors. Multiple input/output device addresses are recognized by the channel-to-channel adapter. The channel-to-channel adapter makes the proper processor-to-processor connection by matching device addresses. In particular, it interconnects for data transfer purposes the two processors for which the same device address has been received. The assignment of device addresses for processor use and the direction of data transfer are by conventions agreed to among the software systems executing on the interconnected processors. The channel-to-channel adapter does not have a view of these conventions. In the more general case, two device addresses are assigned by software convention to each processor-to-processor link, one address being used to transfer data in one direction and the other address being used to transfer data in the opposite direction.