Battery Charging 1.1 specifies that charging devices must dynamically limit bus power current draw during High Speed signalling; 1.2 simply specifies that charging devices and ports must be designed to tolerate the higher ground voltage difference in High Speed signalling. Device classes The functionality of USB devices is defined by class codes, communicated to the USB host to affect the loading of suitable software driver modules for each connected device. Converters also exist that connect PS/2 keyboards and mice (usually one of each) to a USB port. These devices present two HID endpoints to the system and use a microcontroller to perform bidirectional data translation between the two standards.
Recently the power aspects of USB have been extended to cover battery charging as well as AC adapters and other power sources. A tangible benefit of this wide-spread use is the emergence of interchangeable plugs and adapters for charging and powering portable devices. The ability to boot a write-locked SD card with a USB adapter is particularly advantageous for maintaining the integrity and non-corruptible, pristine state of the booting medium. Since charging was never included when this was written, there was no consideration for a device continuing to charge a battery while off, but still attached. This design is USB compatible but does not incorporate BC1.1, so enumeration is required for charging.Other Charge Strategies The landscape for USB battery charging can be complex.
End Of Packet (EOP): is indicated by the transmitter driving 2 bit times of SE0 (D+ and D− both below max.) and 1 bit time of J state. The specification further states, «The USB Icon is also located adjacent to each receptacle. Full-speed (FS) rate of 12 Mbit/s is the basic USB data rate defined by USB 1.0. All USB hubs can operate at this speed. При выполнении этой процедуры будут также стерты данные Стоп кадра (Freeze Frame), в которых содержаться параметры системы, при которых был зафиксирован код неисправности. For mice and keyboards with dual-protocol support, an adaptor that contains no logic circuitry may be used: the hardware in the USB keyboard or mouse is designed to detect whether it is connected to a USB or PS/2 port, and communicate using the appropriate protocol.