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Ethernet Module
MCF5272 ColdFire
®
Integrated Microprocessor User’s Manual, Rev. 3
Freescale Semiconductor
11-11
11.5.1
Ethernet Control Register (ECR)
The ECR register,
, is used to enable/disable the FEC. It is written by the user and cleared at
system reset.
31
26
25
24
16
Field
—
TX_RT
—
Reset
0000_0000_0000_0000
R/W
Read/write
15
2
1
0
Field
—
ETHER_EN RESET
Reset
0000_0000_0000_0000
R/W
Read/write
Addr
MBAR + 0x840
Figure 11-5. Ethernet Control Register (ECR)
Table 11-7. ECR Field Descriptions
Bits
Name
Description
31–26
—
Reserved, should be cleared.
25 TX_RT
Transmit
retime.
0 Normal operation, seven-wire serial mode.
1 The transmit output signals (E_TxD[3:0], E_TxEN, and E_TxER) are delayed by one-half of a
E_TxCLK period. This bit should be set to provide compatibility with transceivers that have hold
time requirements that exceed the MII specification.
24–2
—
Reserved, should be cleared.
1
ETHER_EN Ethernet enable. When this bit is set, the FEC is enabled, and reception and transmission is possible.
When this bit is cleared, reception is immediately stopped and transmission is stopped after a bad
CRC is appended to any frame currently being transmitted. The buffer descriptor(s) for an aborted
transmit frame are not updated following deassertion of ETHER_EN. When ETHER_EN is
deasserted, the DMA, buffer descriptor, and FIFO control logic are reset, including FIFO pointers.
0 RESET
Ethernet
controller
reset. When this bit is set, the equivalent of a hardware reset is performed but it
is local to the FEC. ETHER_EN is cleared and all other FEC registers take their reset values. Also,
any transmission/reception currently in progress is abruptly aborted. This bit is automatically cleared
by hardware once the reset sequence is complete (approximately 16 clock cycles after being set).