Fast Ethernet Controller (FEC)
16-14
Freescale Semiconductor
MCF51CN128 Reference Manual, Rev. 6
16.4.9
Transmit Control Register (TCR)
TCR is read/write and configures the transmit block. This register is cleared at system reset. Bits 2 and 1
must be modified only when ECR[ETHER_EN] is cleared.
2
MII_MODE
Media independent interface mode. Selects the external interface mode for transmit and receive blocks.
0 7-wire mode (used only for serial 10 Mbps)
1 MII mode
1
DRT
Disable receive on transmit.
0 Receive path operates independently of transmit (use for full duplex or to monitor transmit activity in half duplex
mode).
1 Disable reception of frames while transmitting (normally used for half duplex mode).
0
LOOP
Internal loopback. If set, transmitted frames are looped back internal to the device and transmit output signals are
not asserted. The internal bus clock substitutes for the FEC_TXCLK when LOOP is asserted. DRT must be set to
0 when setting LOOP.
Offset: 0x0C4
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
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
RFC_
PAUSE TFC_
PAUSE
FDEN HBC GTS
W
Reset 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
0
0
0
0
Figure 16-10. Transmit Control Register (TCR)
Table 16-12. TCR Field Descriptions
Field
Description
31–5
Reserved, must be cleared.
4
RFC_PAUSE
Receive frame control pause. This read-only status bit is asserted when a full duplex flow control pause frame is
received and the transmitter pauses for the duration defined in this pause frame. This bit automatically clears
when the pause duration is complete.
3
TFC_PAUSE
Transmit frame control pause. Transmits a PAUSE frame when asserted. When this bit is set, the MAC stops
transmission of data frames after the current transmission is complete. At this time, GRA interrupt in the EIR
register is asserted. With transmission of data frames stopped, MAC transmits a MAC Control PAUSE frame.
Next, the MAC clears the TFC_PAUSE bit and resumes transmitting data frames. If the transmitter pauses due
to user assertion of GTS or reception of a PAUSE frame, the MAC may continue transmitting a MAC Control
PAUSE frame.
2
FDEN
Full duplex enable. If set, frames transmit independent of carrier sense and collision inputs. This bit should only
be modified when ECR[ETHER_EN] is cleared.
Table 16-11. RCR Field Descriptions (continued)
Field
Description