SLLSFC6B November 2021 – July 2022 ISOUSB111
The ISOUSB111 device supports Suspend low power state, also called L2 state in the USB 2.0 Link Power Management engineering change notice (ECN). Suspend mode is detected if the bus stays in the LS/FS idle state for more than 3 ms. When Suspend is detected from LS and FS idle state, the ISOUSB111 continues in the LS or FS idle state, at the same time reducing internal power consumption. The transition to the L2 low-power mode is completed within 10 ms.
Exit from L2 occurs through either Resume signaling from the host, on the upstream facing side of ISOUSB111, or Remote Wake signaling from the peripheral on the downstream facing side of ISOUSB111 followed by Resume signaling from the host/hub on the upstream facing side. Start of Resume or Wake are signaled by a ‘K’ state by the host or the device respectively. The end of resume is signalled by the host by driving two low-speed bit times of SE0 followed by a 'J' state. ISOUSB111 is able to replicate the resume and wake signaling appropriately both upstream and downstream. After Resume/Wake signaling the device returns to LS or FS idle state depending on the state it was in before entering the L2 state.