K60P100M100SF2RM Datasheet, PDF (1191/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Chapter 44 10/100-Mbps Ethernet MAC (ENET)
Good pause frames are ignored if ENETn_RCR[FCE] is cleared and are forwarded to the
client interface when ENETn_RCR[PAUFWD] is set.
44.4.4.8 CRC Check
The CRC-32 field is checked and forwarded to the core FIFO interface if
ENETn_RCR[CRCFWD] is cleared and ENETn_RCR[PADEN] is set.
When CRCFWD is set (regardless of PADEN), the CRC-32 field is checked and
terminated (not transmitted to the FIFO).
The CRC polynomial, as specified in the 802.3 standard, is:
• FCS(x) = x³²+ x²⁶+ x²³+ x²²+ x¹⁶+ x¹²+ x¹¹+ x¹⁰+ x⁸+ x⁷+ x⁵+ x⁴+ x²+ x¹+ 1
The 32 bits of the CRC value are placed in the frame check sequence (FCS) field with the
x³¹ term as right-most bit of the first octet. The CRC bits are thus received in the
following order: x³¹, x³⁰,..., x¹, x⁰.
If a CRC error is detected, the frame is marked invalid and RxBD[CR] is set.
44.4.4.9 Frame Padding Removal
When a frame is received with a payload length field set to less than 46 (42 for VLAN-
tagged frames and 38 for frames with stacked VLANs), the zero padding can be removed
before the frame is written into the data FIFO depending on the setting of
ENETn_RCR[PADEN].
Note
If a frame is received with excess padding (i.e. the length field
is set as mentioned above, but the frame has more than 64
octets) and padding removal is enabled, the padding is removed
as normal and no error is reported if the frame is otherwise
correct (e.g. good CRC, less than maximum length, and no
other error).
44.4.5 MAC Transmit
Frame transmission starts when the transmit FIFO holds enough data.
Once a transfer starts, the MAC transmit function performs the following tasks:
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.
1191