MOTOROLA
Chapter 17. Fast Ethernet Controller (FEC)
17-17
Functional Description
To transmit a pause frame, the FEC must operate in full-duplex mode and the user must
assert flow control pause (TCR[TFC_PAUSE]). On assertion of transmit flow control
pause (TCR[TFC_PAUSE]), the transmitter asserts TCR[GTS] internally. When the
transmission of data frames stops, the EIR[GRA] (graceful stop complete) interrupt asserts.
Following EIR[GRA] assertion, the pause frame is transmitted. On completion of pause
frame transmission, flow control pause (TCR[TFC_PAUSE]) and TCR[GTS] are
deasserted internally.
The user must specify the desired pause duration in the OPD register.
Note that when the transmitter is paused due to receiver/microcontroller pause frame
detection, transmit flow control pause (TCR[TFC_PAUSE]) still may be asserted and will
cause the transmission of a single pause frame. In this case, the EIR[GRA] interrupt will
not be asserted.
17.4.11 Inter-Packet Gap (IPG) Time
The minimum inter-packet gap time for back-to-back transmission is 96 bit times. After
completing a transmission or after the backoff algorithm completes, the transmitter waits
for carrier sense to be negated before starting its 96 bit time IPG counter. Frame
transmission may begin 96 bit times after carrier sense is negated if it stays negated for at
least 60 bit times. If carrier sense asserts during the last 36 bit times, it will be ignored and
a collision will occur.
The receiver receives back-to-back frames with a minimum spacing of at least 28 bit times.
If an inter-packet gap between receive frames is less than 28 bit times, the following frame
may be discarded by the receiver.
17.4.12 Collision Handling
If a collision occurs during frame transmission, the Ethernet controller will continue the
transmission for at least 32 bit times, transmitting a JAM pattern consisting of 32 ones. If
the collision occurs during the preamble sequence, the JAM pattern will be sent after the
end of the preamble sequence.
If a collision occurs within 512 bit times, the retry process is initiated. The transmitter waits
a random number of slot times. A slot time is 512 bit times. If a collision occurs after 512
bit times, then no retransmission is performed and the end of frame buffer is closed with a
Late Collision (LC) error indication.
17.4.13 Internal and External Loopback
Both internal and external loopback are supported by the Ethernet controller. In loopback
mode, both of the FIFOs are used and the FEC actually operates in a full-duplex fashion.
Summary of Contents for ColdFire MCF5281
Page 124: ...3 20 MCF5282 User s Manual MOTOROLA EMAC Instruction Set Summary ...
Page 141: ...MOTOROLA Chapter 5 Static RAM SRAM 5 5 SRAM Programming Model ...
Page 142: ...5 6 MCF5282 User s Manual MOTOROLA SRAM Programming Model ...
Page 168: ...6 26 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 186: ...7 18 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 228: ...9 22 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 246: ...10 18 MCF5282 User s Manual MOTOROLA Low Power Wakeup Operation ...
Page 254: ...11 8 MCF5282 User s Manual MOTOROLA Memory Map and Registers ...
Page 264: ...12 10 MCF5282 User s Manual MOTOROLA Chip Select Registers ...
Page 280: ...13 16 MCF5282 User s Manual MOTOROLA Misaligned Operands ...
Page 314: ...14 34 MCF5282 User s Manual MOTOROLA MCF5282 External Signals ...
Page 339: ...MOTOROLA Chapter 15 Synchronous DRAM Controller Module 15 25 SDRAM Example ...
Page 340: ...15 26 MCF5282 User s Manual MOTOROLA SDRAM Example ...
Page 356: ...16 16 MCF5282 User s Manual MOTOROLA DMA Controller Module Functional Description ...
Page 408: ...17 52 MCF5282 User s Manual MOTOROLA Buffer Descriptors ...
Page 446: ...20 24 MCF5282 User s Manual MOTOROLA Interrupts ...
Page 474: ...22 18 MCF5282 User s Manual MOTOROLA Programming Model ...
Page 510: ...23 36 MCF5282 User s Manual MOTOROLA Operation ...
Page 526: ...24 16 MCF5282 User s Manual MOTOROLA I2C Programming Examples ...
Page 672: ...28 12 MCF5282 User s Manual MOTOROLA Functional Description ...
Page 718: ...29 46 MCF5282 User s Manual MOTOROLA Motorola Recommended BDM Pinout ...
Page 750: ...32 8 MCF5282 User s Manual MOTOROLA Ordering Information ...