Abstract: A module type distinguishing apparatus and method for differentiating between modules based upon the presence or absence of a pulling resistor at a specified pin connection of the modules. A high impedance pulling resistance is connected to the line and is subject to sensing while a tri-state mode of operation is initiated in the module. The presence or absence of the pulling resistor in the module is detected and recorded in a register. Differentiation between module types is accomplished based upon the binary state of the data in the register. In a particularized implementation, industry standard L2 cache modules are distinguished as to tag bit size depending on the presence or absence of a pulling resistor as detected during tri-state operation of a tag output pin.

Abstract: A power supply interface suitable to provide voltages of appropriate magnitude to a static random access memory (SRAM) device from a combination of independent sources including a main power supply, an auxiliary power supply, and a battery. The voltages from the interface are at levels consistent with the SRAM modes of operation. During limited voltage tolerance read and write access operations, main power supply voltage is provided through a low forward voltage drop switched metal oxide field effect transistor (MOSFET). Parasitic paths, potentially producible by the transistor and affecting the battery source of power, are eliminated through the use of a second, complementary MOSFET. The second MOSFET is directly responsive to a POWERGOOD signal from the main power supply, indicating both an "on" state and an appropriate voltage level of the main power supply.