Storage Protection in Small Processors
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Typical storage protection mechanisms prohibit one program from inadvertently overlaying its own or other program's storage locations in order to prevent a need to re-Initial Program Load (re-IPL) due to a program wandering off in an uncontrolled manner. On some small computers, storage protection is not implemented due to cost/function tradeoffs. The figure shows an adapter which is connected between the computer's I/O bus and the I/O devices, and which realizes the storage protection objective without the storage protect programming and hardware cost. Hardware Each adapter contains n hardware triggers (called "Allow Bits", one for each device it controls). When an Allow Bit is on, all write operations are rejected. When it is off, all operations work normally.