Self-Clearing Status Register
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
This article describes a circuit arrangement which prevents losing status when clearing a latching status register. A status register in a machine can be made to be either transparent or latching. A transparent status register would always reflect the present status, and a latching status register would remember that a condition occurred after that condition went away. For error conditions a latching status register is much preferred, so that one can see what caused an error after it occurred. The problem with latching status registers is that after the status is read, it must be cleared, so that new status can be latched. This must be done in a way such that no status is lost. Status is lost when a new condition puts a value in the status register between the time it was read and the time it was cleared.