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Fast Ethernet Controller (FEC)
MCF52235 ColdFire® Integrated Microcontroller Reference Manual, Rev. 6
18-44
Freescale Semiconductor
18.5.4.21 Receive Descriptor Ring Start (ERDSR)
The ERDSR is written by the user. It provides a pointer to the start of the circular receive buffer descriptor
queue in external memory. This pointer must be 32-bit aligned; however, it is recommended it be made
128-bit aligned (evenly divisible by 16).
This register is not reset and must be initialized by the user prior to operation.
IPSBAR
Offset: 0x1180 (ERDSR)
Access: User read/write
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
R
R_DES_START
W
Reset
Undefined
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R
R_DES_START
0
0
W
Reset
Undefined
Figure 18-24. Receive Descriptor Ring Start Register (ERDSR)
Table 18-33. ERDSR Field Descriptions
Field
Description
31–2
R_DES_START
Pointer to start of receive buffer descriptor queue.
1–0
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