Advanced-Serial-Port-Monitor_3.png' alt='Transmit 4 Serial Number Mac' title='Transmit 4 Serial Number Mac' />Media independent interface WikipediaRMII redirects here. Aloha Pos Rewards Program there. It is not to be confused with RM2. Transmit 4 Serial Number Mac' title='Transmit 4 Serial Number Mac' />UNIX Serial Port Resources Serial Port Cable Pinouts This content was originally created, collected, and maintained by Stokely Consulting. Users guide for the Pololu Micro Maestro 6channel USB Servo Controller and the Pololu Mini Maestro 12 18 and 24Channel USB Servo Controllers. The media independent interface MII was originally defined as a standard interface to connect a Fast Ethernet i. Mbits media access control MAC block to a PHY chip. The MII is standardized by IEEE 8. PHYs to MACs. Being media independent means that different types of PHY devices for connecting to different media i. Twisted pair copper, fiber optic, etc. MAC hardware. Thus any MAC may be used with any PHY, independent of the network signal transmission media. The MII can be used to connect a MAC to an external PHY using a pluggable connector, or directly to a PHY chip which is on the same PCB. On a PC the CNR connector Type B carries MII bus interface signals. The Management Data InputOutput MDIO serial bus is a subset of the MII that is used to transfer management information between MAC and PHY. At powerup, using autonegotiation, the PHY usually adapts to whatever it is connected to unless settings are altered via the MDIO interface. The original MII transfers data using 4 bit nibbles in each direction 4 transmit data bits, 4 receive data bits. The data is clocked at 2. MHz to achieve 1. Mbits throughput. The original MII design has been extended to support reduced signals and increased speeds. Current variants include, reduced media independent interface RMII, gigabit media independent interface GMII, reduced gigabit media independent interface RGMII, 1. XGMII and serial gigabit media independent interface SGMII. Standard MIIeditThe standard MII features a small set of registers 1Basic Mode Configuration 0Status Word 1PHY Identification 2, 3Ability Advertisement 4Link Partner Ability 5Auto Negotiation Expansion 6The MII Status Word is the most useful datum, since it may be used to detect whether an Ethernet NIC is connected to a network. It contains a bitmask with the following meaning. Capable of 1. 00base. T4. 0x. 78. 00 Capable of 1. HDFD most common. Preamble suppression permitted. Autonegotiation complete. Remote fault. 0x. Capable of Autonegotiation. Link established. Jabber detected. 0x. Extended MII register exist. A more detailed reference on registers exported by MII compatible PHYs can be found looking at the Linux MII interface definition includelinuxmii. Transmitter signalseditSignal name. Description. Direction. TXCLKTransmit clock. PHY to MACTXD0. Transmit data bit 0 transmitted firstMAC to PHYTXD1. Transmit data bit 1. MAC to PHYTXD2. Transmit data bit 2. MAC to PHYTXD3. Transmit data bit 3. MAC to PHYTXENTransmit enable. MAC to PHYTXERTransmit error optionalMAC to PHYThe transmit clock is a free running clock generated by the PHY based on the link speed 2. MHz for 1. 00 Mbits, 2. MHz for 1. 0 Mbits. The remaining transmit signals are driven by the MAC synchronously on the rising edge of TXCLK. This arrangement allows the MAC to operate without having to be aware of the link speed. The transmit enable signal is held high during frame transmission and low when the transmitter is idle. Transmit error may be raised for one or more clock periods during frame transmission to request the PHY to deliberately corrupt the frame in some visible way that precludes it from being received as valid. This may be used to abort a frame when some problem is detected after transmission has already started. The MAC may omit the signal if it has no use for this functionality, in which case the signal should be tied low for the PHY. More recently, raising transmit error outside frame transmission is used to indicate the transmit data lines are being used for special purpose signalling. Specifically, the data value 0b. TXEN low and TXER high is used to request an EEE capable PHY to enter low power mode. Receiver signalseditSignal name. Description. Direction. RXCLKReceive clock. PHY to MACRXD0. Receive data bit 0 received firstPHY to MACRXD1. Receive data bit 1. PHY to MACRXD2. Receive data bit 2. PHY to MACRXD3. Receive data bit 3. PHY to MACRXDVReceive data valid. PHY to MACRXERReceive error. PHY to MACCRSCarrier sense. PHY to MACCOLCollision detect. PHY to MACThe first seven receiver signals are entirely analogous to the transmitter signals, except RXER is not optional and used to indicate the received signal could not be decoded to valid data. The receive clock is recovered from the incoming signal during frame reception. When no clock can be recovered i. PHY must present a free running clock as a substitute. The receive data valid signal RXDV is not required to go high immediately when the frame starts, but must do so in time to ensure the start of frame delimiter byte is included in the received data. Some of the preamble nibbles may be lost. Similar to transmit, raising RXER outside a frame is used for special signalling. For receive, two data values are defined 0b. EEE low power mode, and 0b. The CRS and COL signals are asynchronous to the receive clock, and are only meaningful in half duplex mode. Carrier sense is high when transmitting, receiving, or the medium is otherwise sensed as being in use. If a collision is detected, COL also goes high while the collision persists. In addition, the MAC may weakly pull up the COL signal, allowing the combination of COL high with CRS low which a PHY will never produce to serve as indication of an absentdisconnected PHY. Management signalseditSignal name. Description. Direction. Download A Wireless Lan Based Indoor Positioning Technology Pdf. MDIOManagement data. Bidirectional. MDCManagement data clock. MAC to PHYMDC and MDIO can be shared among multiple PHYs. LimitationseditThe interface requires 1. MDIO and MDC can be shared among multiple PHYs. This presents a problem, especially for multiport devices for example, an eight port switch using MII would need 8  1. For this reason, the reduced media independent interface was developed. Reduced media independent interfaceeditReduced media independent interface RMII is a standard which was developed to reduce the number of signals required to connect a PHY to a MAC. Four things were changed compared to the MII standard to achieve this The two clocks TXCLK and RXCLK are replaced by a single clock. This clock is an input to the PHY rather than an output, which allows the clock signal to be shared among all PHYs in a multiport device, such as a switch. The clock frequency is doubled from 2. MHz to 5. 0 MHz, while the data paths are narrowed to 2 bits rather than 4 bits. RXDV and CRS signals are multiplexed to one signal. The COL signal is removed. These changes mean that RMII uses about half the number of signals compared to MII. The high pin count of MII is more of a burden on microcontrollers with built in MAC, FPGAs, multiport switches or repeaters, and PC motherboard chipsets than it is for a separate single port Ethernet MAC, which partially explains why the older MII standard was more wasteful of pins. RMII signals. Signal name. Description. Direction. REFCLKContinuous 5. MHz Reference Clock may be shared among interfaces. Reference clock may be an input on both devices from an external clock source, or may be driven from the MAC to the PHY. TXD0. Transmit data bit 0 transmitted firstMAC to PHYTXD1. Transmit data bit 1. MAC to PHYTXENWhen high, clock data on TXD0 and TXD1 to the transmitter. MAC to PHYRXD0. Receive data bit 0 received firstPHY to MACRXD1. Receive data bit 1.