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A method to protect a tape and data on it from critical conditions of a tape drive by using a watch dog timer

IP.com Disclosure Number: IPCOM000014560D
Original Publication Date: 2000-Dec-01
Included in the Prior Art Database: 2003-Jun-19
Document File: 1 page(s) / 41K

Publishing Venue

IBM

Abstract

Figure 1 Disclosed is a method to protect a tape and data on it from critical conditions of a tape drive by using a watch dog timer (WDT). A tape needs to be protected from date erasure including servo data and from physical damage like tape breakage when the tape is being used in a tape drive even if CPU or other circuit function becomes abnormal. Figure 1 shows a block diagram of this method. An output signal of WDT is connected to Reset LSI, to Motor Circuit and to CPU. When CPU and other circuit are operating normally, trigger pulses are output from a device (Servo LSI in figure 1). As a result of these pulses, WDT does not assert its output signal.

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  A method to protect a tape and data on it from critical conditions of a tape drive by using a watch dog timer

Figure 1

Disclosed is a method to protect a tape and data on it from critical conditions of a tape drive by using a watch dog timer (WDT).

A tape needs to be protected from date erasure including servo data and from physical damage like tape breakage when the tape is being used in a tape drive even if CPU or other circuit function becomes abnormal.

Figure 1 shows a block diagram of this method. An output signal of WDT is connected to Reset LSI, to Motor Circuit and to CPU. When CPU and other circuit are operating normally, trigger pulses are output from a device (Servo LSI in figure 1). As a result of these pulses, WDT does not assert its output signal.

When operation of the CPU, other LSIs and/or a bus common to CPU and other LSIs become abnormal, Servo LSI can not output a trigger pulse. As a result, WDT assets its output signal. This output signal disables Motor Circuit, then tape motion is stopped. The output signal also activates Reset LSI. The Reset LSI asserts Reset Signal. The Reset Signal resets other LSIs, then write operation is stopped. Physical tape damage is protected by stopping tape motion and data is protected by stopping write operation.

CPU is also reset by the Reset Signal. A special reset is used for this CPU reset. The CPU can detect this special reset. As a result, history of operations before WDT activation is kept on memory. Later...