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Management Data Input/Output (MDIO), also known as Serial Management Interface (SMI) or Media Independent Interface Management (MIIM), is a serial bus defined for the Ethernet family of IEEE 802.3 standards for the Media Independent Interface, or MII. The MII connects media access control (MAC) devices with Ethernet physical layer (PHY ...
Some protocols are NAK-based, meaning that they only respond to messages if there is a problem. Examples include many reliable multicast protocols which send a NAK when the receiver detects missing packets [4] or protocols that use checksums to verify the integrity of the payload and header. Still other protocols make use of both NAKs and ACKs.
Stop (logic high (1)): the next one or two bits are always in the mark (logic high, i.e., 1) condition and called the stop bit(s). They signal to the receiver that the character is complete. Since the start bit is logic low (0) and the stop bit is logic high (1) there are always at least two guaranteed signal changes between characters.
To reduce the number of pins in a package, many ICs use a serial bus to transfer data when speed is not important. Some examples of such low-cost lower-speed serial buses include RS-232, DALI, SPI, CAN bus, I²C, UNI/O, and 1-Wire. Higher-speed serial buses include USB, SATA and PCI Express.
For example, in a computer, address information is transmitted synchronously—the address bits over the address bus, and the read or write strobes of the control bus. Single-wire synchronous signalling. A logical one is indicated when there are two transitions in the same time frame as a zero.
Asynchronous start-stop is the lower data-link layer used to connect computers to modems for many dial-up Internet access applications, using a second (encapsulating) data link framing protocol such as PPP to create packets made up out of asynchronous serial characters. The most common physical layer interface used is RS-232D.
Serial port (COM port) - At one time the most popular method. Serial ports usually lack adequate circuit programming supply voltage. Most computers and laptops newer than 2010 lack support for this port. Socket (in or out of circuit) - the CPU must be either removed from circuit board, or a clamp must be attached to the chip-making access an issue.
Sending data from sub to main may use the opposite clock edge as main to sub. Devices often require extra clock idle time before the first clock or after the last one, or between a command and its response. Some devices have two clocks, one to read data, and another to transmit it into the device. Many of the read clocks run from the chip ...