Serial Communication Controllers (SCCs)
7-258
MC68360 USER’S MANUAL
MOTOROLA
LPB—Loopback Operation
0 = Normal Operation.
1 = Loopback operation. The channel is configured into internal or external loopback
operation as determined by the DIAG bits in the GSMR. For external loopback, the
DIAG bits should be configured for normal operation. For internal loopback, the
DIAG bits should be configured for loopback operation.
SIP—Sample Input Pins
0 = Normal operation.
1 = After the frame is received, the value on the PB15–PB8 pins is sampled and written
to the end of the last receive buffer of the frame. This value is called a tag byte. If
the frame is discarded, the Ethernet:tag byte is also discarded.
LCW—Late Collision Window
0 = The definition of a late collision is any collision that occurs 64 or more bytes from
the preamble.
1 = The definition of a late collision is any collision that occurs 56 or more bytes from
the preamble.
NIB—Number of Ignored Bits
This parameter determines how soon after RENA assertion that the Ethernet controller
should begin looking for the start frame delimiter. In most situations, the user would select
22 bits.
000 = Begin searching for the SFD 13 bits after the assertion of RENA.
001 = Begin searching for the SFD 14 bits after the assertion of RENA.
010 = Begin searching for the SFD 15 bits after the assertion of RENA.
011 = Begin searching for the SFD 16 bits after the assertion of RENA.
100 = Begin searching for the SFD 21 bits after the assertion of RENA.
101 = Begin searching for the SFD 22 bits after the assertion of RENA.
110 = Begin searching for the SFD 23 bits after the assertion of RENA.
111 = Begin searching for the SFD 24 bits after the assertion of RENA.
FDE—Full Duplex Ethernet (Bit 0 of PSMR)
0 = Disable full duplex ethernet mode.
1 = Enable full duplex ethernet.
NOTE
When this bit is set to 1 the LPB bit must also be set to 1.
7.10.23.18 ETHERNET RECEIVE BUFFER DESCRIPTOR (RX BD).
The Ethernet con-
troller uses the Rx BD to report information about the received data for each buffer. Figure
7-71 shows an Ethernet Rx BD example.