Writeable Control Store Protection
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
A method is described which provides user protection when accessing a writeable, shareable Control Store without degrading key performance values. A block diagram of a writeable Control Store (CS) is shown in Fig. 1. The basic method of loading the Control Store is at Initial Program Load (IPL) time by system software. Both read CS and write CS instructions are provided. No protection is needed because the user does not have access to CS during IPL after power-on. Added flexibility can result, however, if the CS can be loaded during run-time by the system or by the user. This flexibility supports machine, customer, or application customization of the function of the card.