![Freescale Semiconductor MCF52230 ColdFire Reference Manual Download Page 302](http://html1.mh-extra.com/html/freescale-semiconductor/mcf52230-coldfire/mcf52230-coldfire_reference-manual_2330648302.webp)
Fast Ethernet Controller (FEC)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
18-33
18.5.4.10 Transmit Control Register (TCR)
The TCR is read/write and is written by the user to configure the transmit block. This register is cleared at
system reset. Bits 2 and 1 should be modified only when ECR[ETHER_EN] equals 0.
IPSBAR
Offset: 0x10C4 (TCR)
Access: User read/write
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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
RFC_
PAUS
E
TFC_
PAUS
E
FDEN HBC
GTS
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 18-13. Transmit Control Register (TCR)
Table 18-22. TCR Field Descriptions
Field
Description
31–5
Reserved, should be cleared.
4
RFC_PAUSE
Receive frame control pause. This read-only status bit is asserted when a full duplex flow control
pause frame has been received and the transmitter is paused 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, the
GRA interrupt in the EIR register is asserted. With transmission of data frames stopped, the MAC
transmits a MAC Control PAUSE frame. Next, the MAC clears the TFC_PAUSE bit and resume
transmitting data frames. If the transmitter is paused 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 are transmitted independent of carrier sense and collision inputs.
This bit should only be modified when ETHER_EN is deasserted.
1
HBC
Heartbeat control. If set, the heartbeat check is performed following end of transmission and the HB
bit in the status register is set if the collision input does not assert within the heartbeat window. This
bit should only be modified when ETHER_EN is deasserted.
0
GTS
Graceful transmit stop. When this bit is set, the MAC stops transmission after any frame that is
currently being transmitted is complete and the GRA interrupt in the EIR register is asserted. If frame
transmission is not currently underway, the GRA interrupt is asserted immediately. After
transmission has completed, a restart can be accomplished by clearing the GTS bit. The next frame
in the transmit FIFO is then transmitted. If an early collision occurs during transmission when GTS
equals 1, transmission stops after the collision. The frame is transmitted again after GTS is cleared.
There may be old frames in the transmit FIFO that are transmitted when GTS is reasserted. To avoid
this deassert ECR[ETHER_EN] following the GRA interrupt.
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:MCF52234CVM60,
MCF52235CVM60