MOD5234-100IR NetBurner Inc, MOD5234-100IR Datasheet - Page 402

• Manufacturer Part Number: MOD5234-100IR
• Description: MOD5234 10/100 ETHERNET MODULE
• Manufacturer: NetBurner Inc
• Type: Controllers & Processorsr

Specifications of MOD5234-100IR

• Interface: I²C, SPI, UART
• Voltage - Supply: 2.5V
• Mounting Type: Surface Mount
• Package / Case: Module
• Product: Modules
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Data Format: -
• Baud Rates: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: Q4483564

Fast Ethernet Controller (FEC)
If a collision occurs during transmission of the frame (half duplex mode), the Ethernet controller
follows the specified backoff procedures and attempts to retransmit the frame until the retry limit
is reached. The transmit FIFO stores at least the first 64 bytes of the transmit frame, so that they
do not have to be retrieved from system memory in case of a collision. This improves bus
utilization and latency in case immediate retransmission is necessary.
When all the frame data has been transmitted, the FCS (Frame Check Sequence or 32-bit Cyclic
Redundancy Check, CRC) bytes are appended if the TC bit is set in the transmit frame control
word. If the ABC bit is set in the transmit frame control word, a bad CRC will be appended to the
frame data regardless of the TC bit value. Following the transmission of the CRC, the Ethernet
controller writes the frame status information to the MIB block. Short frames are automatically
padded by the transmit logic (if the TC bit in the transmit buffer descriptor for the end of frame
buffer = 1).
Both buffer (TXB) and frame (TFINT) interrupts may be generated as determined by the settings
in the EIMR.
The transmit error interrupts are HBERR, BABT, LATE_COL, COL_RETRY_LIM, and
XFIFO_UN. If the transmit frame length exceeds MAX_FL bytes the BABT interrupt will be
asserted, however the entire frame will be transmitted (no truncation).
To pause transmission, set the GTS (graceful transmit stop) bit in the TCR register. When the
TCR[GTS] is set, the FEC transmitter stops immediately if transmission is not in progress;
otherwise, it continues transmission until the current frame either finishes or terminates with a
collision. After the transmitter has stopped the GRA (graceful stop complete) interrupt is asserted.
If TCR[GTS] is cleared, the FEC resumes transmission with the next frame.
The Ethernet controller transmits bytes least significant bit first.
19.3.7 FEC Frame Reception
The FEC receiver is designed to work with almost no intervention from the host and can perform
address recognition, CRC checking, short frame checking, and maximum frame length checking.
When the driver enables the FEC receiver by setting ECR[ETHER_EN], it will immediately start
processing receive frames. When ERXDV is asserted, the receiver will first check for a valid
PA/SFD header. If the PA/SFD is valid, it will be stripped and the frame will be processed by the
receiver. If a valid PA/SFD is not found, the frame will be ignored.
In serial mode, the first 16 bit times of RX_D0 following assertion of ERXDV are ignored.
Following the first 16 bit times the data sequence is checked for alternating 1/0s. If a 11 or 00 data
sequence is detected during bit times 17 to 21, the remainder of the frame is ignored. After bit time
21, the data sequence is monitored for a valid SFD (11). If a 00 is detected, the frame is rejected.
When a 11 is detected, the PA/SFD sequence is complete.
MCF5235 Reference Manual, Rev. 2
19-38
Freescale Semiconductor