Fast Ethernet Controllers (FEC0 and FEC1)
Freescale Semiconductor
26-14
26.4.4
Receive Descriptor Active Registers (RDAR0 & RDAR1)
RDAR
n
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
ECR
n
[ETHER_EN] is also set). After the FEC polls a receive descriptor whose empty bit is not set, FEC
clears the RDAR bit and ceases receive descriptor ring polling until the user sets the bit again, signifying
that additional descriptors are placed into the receive descriptor ring.
The RDAR registers are cleared at reset and when ECR
n
[ETHER_EN] is cleared.
26.4.5
Transmit Descriptor Active Registers (TDAR0 & TDAR1)
The TDAR
n
are command registers which the user writes to indicate the transmit descriptor ring is updated
(transmit buffers have been produced by the driver with the ready bit set in the buffer descriptor).
When the register is written, the TDAR bit is set. This value is independent of the data actually written by
the user. When set, the FEC polls the transmit descriptor ring and processes transmit frames (provided
ECR
n
[ETHER_EN] is also set). After the FEC polls a transmit descriptor that is a ready bit not set, FEC
Table 26-6. EIMR
n
Field Descriptions
Field
Description
31–19
See
Interrupt mask. Each bit corresponds to an interrupt source defined by the EIR
n
register. The corresponding
EIMR
n
bit determines whether an interrupt condition can generate an interrupt. At every processor clock, the
EIR
n
samples the signal generated by the interrupting source. The corresponding EIR
n
bit reflects the state
of the interrupt signal even if the corresponding EIMR
n
bit is set.
0 The corresponding interrupt source is masked.
1 The corresponding interrupt source is not masked.
18–0
Reserved, must be cleared.
Address: 0xFC03_0010 (RDAR0)
0xFC03_4010 (RDAR1)
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
RDAR
0 0 0 0 0 0 0 0 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 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Figure 26-4. Receive Descriptor Active Register (RDAR
n
)
Table 26-7. RDAR
n
Field Descriptions
Field
Description
31–25
Reserved, must be cleared.
24
RDAR
Set to 1 when this register is written, regardless of the value written. Cleared by the FEC device when no additional
empty descriptors remain in the receive ring. Also cleared when ECR
n
[ETHER_EN] is cleared.
23–0
Reserved, must be cleared.
Содержание MCF54455
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