MSC8113 Reference Manual, Rev. 0
25-42
Freescale Semiconductor
Ethernet Controller
25.14 Inter-Packet Gap Time
If a station must transmit, it waits until the LAN becomes silent for a specified period
(inter-packet gap). After a station begins sending, it continually checks for collisions on the LAN.
If a collision is detected, the station forces a jam signal (all ones) on its frame and stops
transmitting. Collisions usually occur close to the beginning of a packet. The station then waits a
random time period (back-off) before attempting to send again. After the back-off completes, the
station waits for silence on the LAN and then begins retransmission on the LAN. This process is
called a retry. If the packet is not successfully sent within a specified number of retries, an error is
indicated. The minimum inter-packet gap time for back-to-back transmission is 96 serial clocks.
The receiver receives back-to-back packets with this minimum spacing. In addition, after waiting
a required number of clocks (based on the back-off algorithm), the transmitter waits for carrier
sense to be deasserted before retransmitting the packet. Retransmission begins 36 serial clocks
after carrier sense is deasserted for at least 60 serial clocks.
25.15 Connecting to Physical Interfaces
This section describes how to use the MIIGSK interface to connect the Ethernet controller to the
PHY/MAC in MII, RMII, and SMII modes. In RMII and SMII mode, some part of the Ethernet
controller signals are used. Table 25-4 indicates which signals are reserved in these modes and
which signals should not be connected.
Note:
The MAC-to-MAC connection is not defined in the IEEE
Std. 802.3
. Care must be
taken to ensure that the receive side has enough set-up and hold time.
CRC error
If a CRC error occurs, the controller sets RxBD[CR], closes the buffer, and sets IEVENT[RXFn]. This
Ethernet controller relies on the statistics collector block to record the event. After receiving a frame with a
CRC error, the receiver then enters hunt mode.
Memory Read
Error
A system bus error occurred during a DMA transaction. The controller sets IEVENT[EBERR] and discards
the frame and increments the discarded frame counter (DISFC). In addition, the proper RSTAT halt bit is
set. (For four queues, only the queue that encountered the error halts.) The halted queue resumes reception
once its RSTAT halt bit is cleared.
RIFGSI
While receiving IFG segments in SMII Mode the received IFG segments are sampled to the MIGSK_RIFGR.
If there is a difference between a received inter-frame gap bit (or more) in the MIIGSK_RIFBR register and
its corresponding bit in the MIIGSK_ERIFBR register then the corresponding bit in the MIIGSK_IEVENT
register is set.
If it is also enabled in the corresponding bit in the MIIGSK_IMASK register then RIFGSI interrupt is set.
Table 25-16. Reception Errors (Continued)
Type Of Error
Ethernet Controller Operation
Содержание MSC8113
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