Fast Ethernet Controller (FEC)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
Freescale Semiconductor
18-25
18.5.4.3
Receive Descriptor Active Register (RDAR)
RDAR is a command register that indicates that the receive descriptor ring has been updated (empty
receive buffers have been produced by the driver 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 process receive frames (provided
ECR[ETHER_EN] is also set). After the FEC polls a receive descriptor whose empty bit is not set, then
the FEC clears the RDAR bit and cease receive descriptor ring polling until the user sets the bit again,
signifying that additional descriptors have been placed into the receive descriptor ring.
The RDAR register is cleared at reset and when ECR[ETHER_EN] is cleared.
IPSBAR
Offset: 0x1010 (RDAR)
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
R_DE
S_AC
TIVE
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
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 18-6. Receive Descriptor Active
Register (RDAR)
Table 18-14. RDAR Field Descriptions
Field
Description
31–25
Reserved, should be cleared.
24
R_DES_ACTIVE
Set to one 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[ETHER_EN] is cleared.
23–0
Reserved, should be cleared.
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