US 4,734,851 AGranted

Write protect control circuit for computer hard disc systems

OwnerDennis Directorinventor

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Abstract

A write protect system prevents inadvertent attempts to write data into a permanent memory storage device (such as a disc drive) containing valuable data that might be destroyed by such a write attempt. The write protect system includes a controller coupled to at least one memory storage device via information transfer busses and a control data bus. The controller sends signals for writing data into selected ones of memory devices. A circuit is coupled into the control data bus for monitoring signals transmitted thereover. Responsive to the monitoring circuit, access is barred to preclude writing into a specific one of the memory devices whereby data may not be accidentally written into the specific memory. The barring is cancelled if a specific action is taken whereby data may be deliberately written into a specific memory.

Claims3

Dependent claims

A write protect system comprising:

a computer having at least one memory means, said memory means including a hard disc drive,
a controller coupled to said hard disc drive by at least one information transfer bus and at least one control data bus,
means for selecting said hard disc drive for operation by sending a signal from said controller to said hard disc drive on a first wire in said control data bus,
means for enabling said hard disc drive to erase data in said hard disc drive by sending a signal from said controller to said hard disc drive on a second wire in said control data bus,
circuit means coupled to said control data bus for monitoring signals transmitted on said first wire in said control data bus,
guard means for selectively interrupting the signal from said enabling means on the second wire to prevent said hard disk drive from being enabled to erase data thereby preventing data from being accidentially erased from said hard disc drive,
said guard means including a plurality of logic devices, at least one of said logic devices having an output coupled to said hard disc drive and at least one of said logic devices having an input coupled to said enabling means by connection to said second wire, and a manual switch coupled to said logic devices for controlling the logic states of said logic devices to enable gating of the signal from the enabling means responsive to the manual switch,
whereby data cannot be erased from said hard disc drive when said manual switch is in a selected write protect state.

5 more elements

Dependencies are inferred from the claim text.