Cisco Systems GRP-B manual MII Connections, Pin Signal Input Output Input/Output Description

Replacing a GRP

MII Connections

The MII connection requires an external physical sublayer (PHY) and an external transceiver. Depending on the type of media you use between the MII connection on the GRP and your switch or hub, the network side of your 100BASE-T transceiver should be appropriately equipped—with SC-type or ST-type connectors (for optical fiber), BNC connectors, and so forth. Figure 9 shows the pin orientation of the female MII receptacle on GRP.

The MII receptacle uses two screw-type locks, called jackscrews (see Figure 9), to secure the cable or transceiver to the MII port. MII cables and transceivers have knurled thumbscrews (screws that you can tighten with your fingers) that you fasten to the jackscrews on the GRP’s MII connector. Use the jackscrews to provide strain relief for your MII cable. (The RJ-45 modular plug has strain relief functionality incorporated into the design of its standard plastic connector.)

Figure 9 MII Receptacle (Horizontal Orientation)

Pin 1

H6538

Jackscrew Pin 21

Table 5 lists the MII connector pinout and signals. MII cables and transceivers are not available from Cisco Systems, but are available commercially.

Table 5 MII Receptacle Pinout

Pin1	Signal	Input	Output	Input/Output	Description
14 to 17	TxD	—	Yes	—	Transmit Data
12	Tx_CLK	Yes	—	—	Transmit Clock2
11	Tx_ER	—	Yes	—	Transmit Error
13	Tx_EN	—	Yes	—	Transmit Enable
3	MDC	—	Yes	—	MII Data Clock
4 to 7	RxD	Yes	—	—	Receive Data
9	Rx_CLK	Yes	—	—	Receive Clock
10	Rx_ER	Yes	—	—	Receive Error
8	Rx_DV	Yes	—	—	Receive Data Valid
18	COL	Yes	—	—	Collision
19	CRS	Yes	—	—	Carrier Sense
2	MDIO	—	—	Yes	MII Data
					Input/Output
22 to 39	GND	—	—	—	Common ground
1, 20, 21, 40	V	—	—	—	+5.0 VDC

1.Any pins not indicated are not used.

2.The signals Tx_CLK and Rx_CLK are generated by the external transceiver.

Connecting to the Ethernet Port

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