External Register Error Testing
Original Publication Date: 1979-Apr-01
Included in the Prior Art Database: 2005-Feb-20
External registers are the means by which a microprocessor communicates with external apparatus. Each register within a functional area has a unique address identifying a particular register and is addressed via an address bus driven by the microprocessor. The addressed external register will be selected if the functional area decodes the address of that register and the parity is correct. If the parity is incorrect, no register will be selected, and an error is indicated. When selected, the functional area activates a line to a maintenance area to indicate which functional area has a register actively attached to the external register bus. Data is transferred over data buses which are used for reading and writing the data.