USB A METHOD AND APPARATUS FOR USB SIGNALING VIA INTERMEDIATE TRANSPORTS

摘要

According to one aspect of the invention, the system comprises first and second modules settled at the host side and the device side end of the relay transmission link, respectively, connecting the USB host to the USB device. The system detects when the host activates isochronous termination in the device for isochronous IN data transactions, and the second module generates a data request for the device itself and outputs isochronous data output from the device toward the first module. Forward it. In turn, the first module buffers the data and provides it in response to the host's data request. However, the first module blocks host requests from propagating to the device and NACKs the host requests until data forwarded from the second module becomes available. This operation allows the host and device to avoid USB timing violations even when extending the relay transmission link.