Dual mode USB-PS/2 device

What is this patent about?

'201 is related to the field of peripheral device interfaces, specifically addressing the need for devices to communicate using either the Universal Serial Bus (USB) or the Personal System/2 (PS/2) protocol. Traditionally, supporting both protocols required separate external components and complex microcontroller firmware, leading to increased cost, board space, and compromised performance.

The underlying idea behind '201 is to integrate the USB and PS/2 interface logic into a single integrated circuit, enabling automatic protocol selection based on the connected bus. This eliminates the need for external components and dedicated I/O pins, simplifying the design and reducing the complexity of the required firmware. The key is a dual-mode interrupt detection circuit and a dual-mode driver circuit within the IC.

The claims of '201 focus on an apparatus comprising an integrated circuit configured to operate in a plurality of signaling protocols. The integrated circuit is further configured to automatically select one of the plurality of signaling protocols in response to a signaling protocol of a connected bus.

In practice, the integrated circuit monitors the data lines (DP/SCLK and DM/SDATA) for specific signaling patterns indicative of either USB or PS/2. A MODE signal controls the selection of the active protocol. The dual-mode interrupt detection circuit generates an interrupt signal (INT) based on the detected protocol, triggering the appropriate communication behavior. The dual-mode driver circuit then handles the actual data transmission and reception according to the selected protocol.

This approach differs from prior solutions by integrating all necessary components into a single chip. It avoids the need for external level shifters or protocol converters. Furthermore, the invention incorporates features like controlled edge rates for low-emissions operation and a tri-stateable regulator pin to simplify mode switching, offering a more efficient and cost-effective solution for dual-mode peripheral devices.