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TXD[3:0] Transmit Data

RXD[3:0] Receive Data

TX_EN Transmit Enable

RX_DV Receive Data Valid

TX_ERR Transmit Error

RX_ERR Receive Error

COL Collision Detect

CRS Carrier Sense

CLK_TX Transmit Clock

CLK_RX Receive Clock

Figure 2 shows the connections between the DS34T108 and a generic Ethernet PHY in RMII mode. Here, the pin count

has been reduced to 8 signals with the Tx data and Rx data being transmitted synchronously with respect to a REF_CLK.

In this case, the REF_CLK is CLK_TX. Please note there are only two data pins in RMII mode instead of the four data pins

used in MII mode. This is done solely by doubling the CLK frequency from 25MHz to 50MHz. The two data bits at 50MHz

enable RMII mode to achieve a throughput of 100Mb.

Figure 2. The DS34T108 is connected to an Ethernet PHY in RMII mode.

TXD[1:0] Transmit Data

RXD[1:0] Receive Data

TX_EN Transmit Enable

RX_DV Carrier Sense/Receive Data Valid

RX_ERR Receive Error

CLK_TX Transmit Clock

In RMII mode, collision detection (COL) is not performed by the PHY, while transmit error is eliminated all together. It is

assumed that RMII is used only for chip-to-chip communications and you will, therefore, not have a transmit error.

However, carrier sense and receive data valid (RX_DV) are multiplexed into the same signal.

The DS34T108 device supports both MII and RMII modes of operation. To configure the device in MII mode, simply select

bits [15:14] of the General_cfg_reg0 (0x0000000) to 00b; when selecting RMII mode, change these same bits to 01b. No

other operation is required. Any other configuration for the PHY must be done externally.

Q3. What is a bundle in TDMoIP products?

A3. A bundle is defined as a stream of bits that have originated from the same physical interface and are transmitted

from a TDMoIP source device to a TDMoIP destination device. For example, bundles may be composed of any number of

64kbps timeslots originating from a single T1/E1 or an entire T3/E3. Bundles are single-direction streams, frequently

coupled with bundles in the opposite direction to enable full-duplex communications. More than one bundle can be

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