Freescale Semiconductor MPC8260 - Manual (Page 788)

SCC Ethernet Mode
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
25-4 Freescale Semiconductor
25.3 Connecting the PowerQUICC II 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 PowerQUICC II.
• Transmit clock (TCLK)—a CLKx signal routed through the bank of clocks on the PowerQUICC II.
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 PowerQUICC II TXD signal.
• Receive data (RXD)—the PowerQUICC II 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 PowerQUICC II and EEST.
Figure 25-3. Connecting the PowerQUICC II to Ethernet
The EEST has similar names for its connection to the above seven PowerQUICC II signals. The EEST also
provides a loopback input so the PowerQUICC II can perform external loopback testing, which can be
controlled by any available PowerQUICC II parallel I/O signal. The passive components needed to
PowerQUICC II EEST
MC68160
TXD
TENA (RTS)
TCLK (CLK x )
RXD
RENA (CD)
RCLK (CLK x )
CLSN (CTS)
Parallel I/O
Tx
TENA
TCLK
Rx
RENA
RCLK
CLSN
Loop
Passive
Passive
Twisted
Pair
AUI
Preamble
Start Frame
Data
Delimiter
Destination
Address
Type/
Length
Source
Address
Frame Check
Sequence
7 Bytes 1 Byte 6 Bytes 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 PowerQUICC II.
(Pads)