1. Field of the Invention
The present invention relates to a fetching method, and more particularly, to a fetching method for accurately fetching the identifications of the SCSI (Small Computer Systems Interface) equipment even under the circumstances interrupted by ESD (Electro-Static Discharge).
2. Description of the Prior Art
Nowadays, there are many computer equipment such as hard disks and CD-ROMs (Compact Disk Read Only Memory) following the SCSI standard. However, each of the SCSI equipment needs a unique identification for recognizing and fetching their information in a computer system.
There usually appears unexpected ESD (Electro-Static Discharge) in the natural world, which usually generates large momentary current. FIG. 2 illustrates the relationship between time and the momentary current caused by the ESD, and the FIG. 3 lists four ESD levels of the momentary currents. It is obvious that the momentary current will rise to the first peak in a range about 0.7 to 1.0 ns (Nano second) whatever its level is, and the momentary current falls down as time passing. For example, an ESD with 4 KV (Kilo Volt) will generate a momentary current with the first peak of about 15 amperes (point A in the FIG. 2). Furthermore, when the time interval starts from the ESD appearance moment to 30 ns (point B in the FIG. 2) and 60 ns (point C in the FIG. 2) later, the momentary current falls down to 8 and 4 amperes, respectively. Please note that the momentary current increases as the voltage of the ESD becomes large.
Those sensitive computer systems are usually interrupted by the ESD, and thus cause unexpected failures. For example, while the computer system fetches the identification of SCSI equipment, a wrong SCSI identification may be fetched under the situation influenced by the ESD. To overcome this disadvantage, a conventional scheme is to apply a shield to cover the SCSI equipment and therefore redirects the momentary current to a proper place (e.g., to ground). Unfortunately, the shield can not always prevent the SCSI equipment from influencing by the ESD especially when the shield is broken. A requirement has been arisen to disclose a method for accurately fetching the identification of the SCSI equipment anytime.