K60P100M100SF2RM Datasheet, PDF (1187/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Discard
Discard
Discard
Discard
Chapter 44 10/100-Mbps Ethernet MAC (ENET)
Detect Preamble
Collision
Half duplex only
Compare destination address
with local/multicast/broadcast
Discriminate length/type
information
Receive payload
Remove padding
Verify CRC
Verify frame length
Write data FIFO
and frame status
Figure 44-55. MAC Receive Flow
44.4.4.1 Collision Detection in Half Duplex Mode
If the packet is received with a collision detected during reception of the first 64 bytes,
the packet is discarded (if frame size was less than ~14 octets) or transmitted to the user
application with an error and RxBD[CE] set.
44.4.4.2 Preamble Processing
The IEEE 802.3 standard allows a maximum size of 56 bits (seven bytes) for the
preamble, while the MAC core allows any arbitrary preamble length.
The MAC core checks for the start frame delimiter (SFD) byte. If the next byte of the
preamble, which is different from 0x55, is not 0xD5, the frame is discarded.
Although the IEEE specification specifies that frames should be separated by at least 96
bits (inter-packet gap), the MAC core is designed to accept frames only separated by 64
MII (10/100 Mbps operation) bits.
The MAC core removes the preamble and SFD bytes.
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
1187