HARDWARE PROTECTION CONTROL FOR COMPUTER STORAGE DEVICES

摘要

A write protect device for a computer comprising a hardware circuit with a switch connected to an internally installed circuit card which has cable connections between data storage device drives and a drive controller cable, the circuit card intercepting control lines used for drive selection and control. The switch is connected to inputs of a latch circuit which, in one position of the switch, generates *READONLY and READONLY signals at outputs of the latch circuit and *DISABLE and DISABLE signals at other outputs when the switch is placed in a second position. The circuit card includes an inverter and a NAND gate in a *WRITE GATE line to the data storage device drives with one input of the NAND gate being connected to the *READONLY line from the latch circuit which will prevent any *WRITE GATE signal from reaching the data storage device drives when the *READ ONLY line is activated to place the computer in a read only mode. A further inverter and a NAND gate intercepts a *DRIVE SEL line to the data storage device drives with the NAND gate having one input connected to the *DISABLE line from the latch circuit. When the *DISABLE line is activated, that NAND gate will prevent any *DRIVE SEL signal from reaching an associated data storage device drive and place the computer in a drive protected mode. A number of internal optional links and NAND gates on the circuit card can create further selectable operational features for the computer such as an object reuse feature which, when enabled, will prevent any changes in the switch position from changing an operational mode until after the computer is "reset".