Personal computer (PCs) may be provided with one of a number of architectures. One popular architecture is the so-called ISA (Industry Standards Association) bus type PC. As the name implies, a PC having an ISA bus architecture may be designed around particular system bus format. The ISA bus architecture is a public domain architecture for a computer system agreed upon by a number of computer and component manufacturers called the Industry Standards Association.
Other types of architectures have been promoted as successors to the ISA bus format, providing enhanced features such an increased I/O speed and peripheral device identification. The EISA and PCI bus designs are two examples of newer bus designs. For a computer component manufacturer, variations in bus types may pose design difficulties, as a given computer component (e.g., logical device) may be desirable for use with a number of different architectures.
Manufacturing separate components compatible with different bus designs may be costly in terms of both manufacturing and inventory. Moreover, components specially design for one bus design reduce the interchangability of components which made the original ISA bus design successful.
In particular, in the ISA bus design, a reset signal (i.e., power on reset or reboot) may use an active high signal (e.g. logic level 1) whereas a PCI bus design may use an active logic low (e.g., logic level 0) for a reset signal. Thus, in order to incorporate a semiconductor circuit into, for example, an add-on board for a PC, it may be necessary to reconfigure the logic level of the reset signal. DIP switches, jumpers or the like may be utilized to provide a manual technique for reconfiguring a reset signal for different bus applications. However, such devices add costly circuitry to an add-on board or additional pins for a semiconductor device and in addition may require an additional reconfiguration step by the user.
Even if a device is configured manually using DIP switches, jumpers or the like, during a power on cycle a power on signal, either Vdd or Vcc power supply may be unstable during the first few microseconds, milliseconds, or even first hundred milliseconds. Power may be dropped due to parasitic inductance on the motherboard, ground noise or power noise. During a power-on cycle, a power supply may not be stable, and thus logic levels (0 and 1) may be difficult to detect.