Motorola MPC823e - Page 776

Communication Processor Module
16-322 MPC823e REFERENCE MANUAL MOTOROLA
SCCs
COMMUNICATION
16
PROCESSOR MODULE
Figure 16-108 illustrates the basic components and pins required to make the Ethernet
connection between the MPC823e and EEST.
The following pins function differently when a serial communication controller is in Ethernet
mode than when it is in other protocols:
• Transmit Enable (TENA)—The RTSx
pin changes to TENA when a serial
communication controller is in Ethernet mode. The polarity of TENA is active high,
whereas the polarity of RTSx
is active low.
• Receive Enable (RENA)—The CDx
pin changes to RENA when a serial communication
controller is in Ethernet mode. The polarity of RENA is active high, whereas the polarity
of CDx
is active low.
• Collision (CLSN)—The CTSx
pin changes to CLSN when a serial communication
controller is in Ethernet mode. The polarity of CLSN is active high, whereas the polarity
of CTSx
is active low.
MPC823e
Figure 16-107. Connecting the MPC823e to Ethernet
Note: The carrier sense signal is referenced in Ethernet descriptions because it
indicates when the LAN is being used. Carrier sense is defined as RENA OR’ed
with CLSN.
MPC823
RJ-45
SCCx
TXDx
TENA (RTSx)
TCLK (CLKx)
RXDx
RENA (CDx)
RCLK (CLKx)
CLSN (CTSx)
PARALLEL I/O
TX
TENA
TCLK
RX
RENA
RCLK
CLSN
LOOP
D-15
TWISTED PAIR
AUI
PASSIVEPASSIVE
EEST
MC68160
PREAMBLE
FRAME
CHECK
SEQUENCE
START
FRAME
DELIMITER
DATA
7 BYTES 1 BYTE
46–1500 BYTES
DEST
ADDR
SOURCE
ADDR
6 BYTES 2 BYTES
TYPE/
LENGTH
6 BYTES
4 BYTES
STORED IN TRANSMIT BUFFER
STORED IN RECEIVE BUFFER
NOTE: The MPC82x automatically pads the short transmit frames.