Motorola MPC823e - Page 774

Communication Processor Module
16-320 MPC823e REFERENCE MANUAL MOTOROLA
COMMUNICATION
16
PROCESSOR MODULE
SCCs
16.9.22.2 ETHERNET ON THE MPC823e. When the MODE field in the general SCCx
mode low register (GSMR_L) selects an SCCx to be in Ethernet mode, the serial
communication controllers perform the full set of IEEE 802.3/Ethernet CSMA/CD media
access control and channel interface functions. In this manual, a serial communication
controller in Ethernet mode is also referred to as an SCCx Ethernet controller.
The SCCx Ethernet controller requires an external serial interface adaptor (SIA) and
transceiver function to complete the interface to the media. This function is implemented in
the Motorola MC68160 enhanced Ethernet serial transceiver (EEST).
The MPC823e+EEST solution provides a direct connection to the attachment unit interface
(AUI) or twisted-pair (10BASE-T). The EEST provides a glueless interface to the MPC823e,
Manchester encoding and decoding, automatic selection of 10BASE-T versus AUI ports,
10BASE-T polarity detection and correction, LED drivers, and a low-power mode. For more
information, refer to the MC68160 device documentation.
The SCCx Ethernet controller also provides a number of features. Although the MPC823e
contains DPLLs that allow Manchester encoding and decoding, these DPLLs were not
designed for Ethernet rates. Therefore, the SCCx Ethernet controller bypasses the on-chip
DPLLs and uses the external system interface adaptor on the EEST instead.
Figure 16-106. Ethernet Block Diagram
SHIFTER
RECEIVE
RECEIVER
CONTROL
UNIT
FIFO
SHIFTER
TRANSMIT
TRANSMITTER
CONTROL
UNIT
FIFO
SLOT TIME
CLOCK
GENERATOR
INTERNAL CLOCKS
CONTROL
REGISTERS
TXDx
RXDx
PERIPHERAL BUS
U-BUS
DATADATA
RX CLOCK
TX CLOCK
AND DEFER
COUNTER
RTSx = TENA
RANDOM NO.
CDx = RENA
CTSx = CLSN
CTSx = CLSN
CDx = RENA