Standard Microsystems Corporation

Jeffrey C Dunnihoo

Richard E Wahler

J Glen Rockford

The present invention relates to a peripheral microcontroller for providing a high performance USB (Universal Serial Bus) connection to existing peripheral architectures (such as printers and disk drives with existing microcontrollers) and to new peripheral architectures (such as a 4-port USB-to-Ethernet Bridge). The USB peripheral microcontroller includes three units. A Serial Interface Engine (SIE) connects to a USB host or USB hub. A Microcontroller (MCU) Interface Unit connects to one or more peripheral devices such as ISA-like peripherals. A Memory Management Unit (MMU) provides a buffering mechanism between the SIE and MCU Interface Unit. The MMU utilizes a unique data packet buffering architecture. Packets received at the MMU from a peripheral for transmission to the USB host and packets received at the MMU from the USB host for transmission to a peripheral are buffered in a RAM. The capacity of the RAM is dynamically allocatable among various USB endpoints and the USB host so that the size of the RAM is minimized. The data path of the inventive USB peripheral controller is also highly advantageous. The SIE accesses the packet buffer RAM via a DMA controller in the MMU. The MCU Interface Unit accesses the packet buffer RAM via a microcontroller or a DMA controller. An arbiter in the MMU enables these multiple masters to access the packet buffer RAM.

Dynamically allocating space in RAM shared between multiple USB endpoints and USB host

An interface that allows the host CPU and the keyboard controller in a PC to share a common BIOS ROM includes a logic circuit that receives a set of input signals and produces a set of signals that emulates a jump instruction op-code that causes the host CPU to vector to a specified address location in the system memory map normally reserved for the system ROM BIOS code, whenever both the host CPU and keyboard controller are contending for access to the BIOS ROM.

Shared bios ROM warm boot

A process and apparatus for reducing power consumption in processor-based system by interrupting the main system power supply during periods of inactivity. Existing input/output circuitry is powered from a constant auxiliary power source to monitor system interrupts which are used to generate power events that control the on/off state of the main system power supply.

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Austin, TX, United States of America

Jeffrey C Dunnihoo