Fast Ethernet Controller (FEC)
16-10
Freescale Semiconductor
MCF51CN128 Reference Manual, Rev. 6
16.4.5
Ethernet Control Register (ECR)
ECR is a read/write user register, though hardware may alter fields in this register as well. The ECR
enables/disables the FEC.
16.4.6
MII Management Frame Register (MMFR)
The MMFR is user-accessible and does not reset to a defined value. The MMFR register is used to
communicate with the attached MII compatible PHY device(s), providing read/write access to their MII
registers. Performing a write to the MMFR causes a management frame to be sourced unless the MSCR is
programmed to 0. If MSCR is cleared while MMFR is written and then MSCR is written with a non-zero
value, an MII frame is generated with the data previously written to the MMFR. This allows MMFR and
MSCR to be programmed in either order if MSCR is currently zero.
24
TDAR
Set to 1 when this register is written, regardless of the value written. Cleared by the FEC device when no additional
ready descriptors remain in the transmit ring. Also cleared when ECR[ETHER_EN] is cleared.
23–0
Reserved, must be cleared.
Offset: 0x024
Access: User read/write
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
R 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ETHER
_EN
RESET
W
Reset 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0
0
Figure 16-6. Ethernet Control Register (ECR)
Table 16-7. ECR Field Descriptions
Field
Description
31–2
Reserved, must be cleared.
1
ETHER_EN
When this bit is set, FEC is enabled, and reception and transmission are possible. When this bit is cleared,
reception immediately stops and transmission stops after a bad CRC is appended to any currently transmitted
frame. The buffer descriptor(s) for an aborted transmit frame are not updated after clearing this bit. When
ETHER_EN is cleared, the DMA, buffer descriptor, and FIFO control logic are reset, including the buffer descriptor
and FIFO pointers. Hardware alters the ETHER_EN bit under the following conditions:
• ECR[RESET] is set by software, in which case ETHER_EN is cleared
• An error condition causes the EIR[EBERR] bit to set, in which case ETHER_EN is cleared
0
RESET
When this bit is set, the equivalent of a hardware reset is performed but it is local to the FEC. ECR[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 during the reset sequence. The reset sequence
takes approximately eight internal bus clock cycles after this bit is set.
Table 16-6. TDAR Field Descriptions (continued)
Field
Description
