MPC8280 datasheet(792/1386 Pages) FREESCALE

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SCC Ethernet Mode

MPC8280 PowerQUICC II Family Reference Manual, Rev. 1

25-4

Freescale Semiconductor

25.3

Connecting the MPC8280 to Ethernet

The basic interface to the external SIA chip consists of the following Ethernet signals:

•

Receive clock (RCLK)—a CLKx signal routed through the bank of clocks on the MPC8280.

•

Transmit clock (TCLK)—a CLKx signal routed through the bank of clocks on the MPC8280. Note

that RCLK and TCLK should not be connected to the same CLKx since the SIA provides separate

transmit and receive clock signals.

•

Transmit data (TXD)—the MPC8280 TXD signal.

•

Receive data (RXD)—the MPC8280 RXD signal.

The following signals take on different functionality when the SCC is in Ethernet mode:

•

Transmit enable (TENA)—RTS becomes TENA. The polarity of TENA is active high, whereas the

polarity of RTS is active low.

•

Receive enable (RENA)—CD becomes RENA.

•

Collision (CLSN)—CTS becomes CLSN. The carrier sense signal is referenced in Ethernet

descriptions because it indicates when the LAN is in use. Carrier sense is defined as the logical OR

of RENA and CLSN.

Figure 25-3. shows the basic components and signals required to make an Ethernet connection between

the MPC8280 and EEST.

Figure 25-3. Connecting the MPC8280 to Ethernet

The EEST has similar names for its connection to the above seven MPC8280 signals. The EEST also

provides a loopback input so the MPC8280 can perform external loopback testing, which can be controlled

by any available MPC8280 parallel I/O signal. The passive components needed to connect to AUI or

MPC8280

EEST

MC68160

TXD

TENA (RTS)

TCLK (CLKx)

RXD

RENA (CD)

RCLK (CLKx)

CLSN (CTS)

Parallel I/O

TENA

TCLK

RENA

RCLK

CLSN

Loop

Passive

Twisted

Pair

AUI

Preamble

Start Frame

Data

Delimiter

Destination

Address

Type/

Length

Source

Address

Frame Check

Sequence

7 Bytes

1 Byte

6 Bytes

2 Bytes

46–1500 Bytes

4 Bytes

Stored in Receive Buffer

RJ-45

D-15

Stored in Transmit Buffer

SCC

NOTE: Short Tx frames are padded automatically by the MPC8280.

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