USB RAM device with buffer descriptor table and dynamically configurable endpoint allocation

摘要

A compound USB device has a controller and a N+1 component USB devices. Each component USB device Ci is assigned Ei endpoints, where 0≦i≦N and where each component USB device is assigned at least as many endpoints as required by its functionality. At least one component USB device is assigned the maximum number endpoints. At least one other component USB device is assigned the minimum number of endpoints, which is less than the maximum. The controller includes a RAM-share subsystem with a RAM module. The RAM module includes a USB RAM segment that has a buffer descriptor (BD) table and an endpoint data buffer. The BD table includes a corresponding entry for each assigned endpoint. At least a portion of the USB RAM segment is assigned for non-USB uses.

主权项

1. A compound universal serial bus (USB) microcontroller comprising:
a random-access memory (RAM) share subsystem comprising:
a serial interface engine;a RAM module including a USB RAM comprising (i) a buffer descriptor (BD) table and (ii) an endpoint data buffer; anda processor core; a plurality of component USB devices, wherein:
each component USB device is assigned a corresponding set of endpoints;the BD table comprises a plurality of entries corresponding to the endpoints assigned to the component USB devices, each entry including status and control information for the corresponding endpoint;a first component USB device is assigned a maximum number of endpoints; anda second component USB device is assigned a minimum number of endpoints that is less than the maximum number of endpoints.