Fast Ethernet Controller (FEC)
16-8
Freescale Semiconductor
MCF51CN128 Reference Manual, Rev. 6
16.4.2
Interrupt Mask Register (EIMR)
The EIMR register controls which interrupt events are allowed to generate actual interrupts. All
implemented bits in this CSR are read/write. A hardware reset clears this register. If the corresponding bits
in the EIR and EIMR registers are set, an interrupt is generated. The interrupt signal remains asserted until
a 1 is written to the EIR bit (write 1 to clear) or a 0 is written to the EIMR bit.
16.4.3
Receive Descriptor Active Register (RDAR)
RDAR is a command register, written by the user, indicating the receive descriptor ring is updated (the
driver produced empty receive buffers with the empty bit set).
When the register is written, the RDAR bit is set. This is independent of the data actually written by the
user. When set, the FEC polls the receive descriptor ring and processes receive frames (provided
20
RL
Collision retry limit. Indicates a collision occurred on each of 16 successive attempts to transmit the frame. The frame
is discarded without being transmitted and transmission of the next frame commences. This error can only occur in
half duplex mode.
19
UN
Transmit FIFO underrun. Indicates the transmit FIFO became empty before the complete frame was transmitted. A
bad CRC is appended to the frame fragment and the remainder of the frame is discarded.
18–0
Reserved, must be cleared.
Offset: 0x008
Access: User read/write
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
HB
ERR
BABR BABT GRA
TXF
TXB
RXF
RXB
MII
EB
ERR
LC
RL
UN
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
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 16-3. Ethernet Interrupt Mask Register (EIMR)
Table 16-4. EIMR Field Descriptions
Field
Description
31–19
See
Interrupt mask. Each bit corresponds to an interrupt source defined by the EIR register. The corresponding
EIMR bit determines whether an interrupt condition can generate an interrupt. At every processor clock, the
EIR samples the signal generated by the interrupting source. The corresponding EIR bit reflects the state of
the interrupt signal even if the corresponding EIMR bit is set.
0 The corresponding interrupt source is masked.
1 The corresponding interrupt source is not masked.
18–0
Reserved, must be cleared.
Table 16-3. EIR Field Descriptions (continued)
Field
Description