Motorola MPC8260 用户手册
28-8
MPC8260 PowerQUICC II UserÕs Manual
MOTOROLA
Part IV. Communications Processor Module
Fields in the TODR are described in Table 28-4
28.6 FCC Buffer Descriptors
Data associated with each FCC channel is stored in buffers. Each buffer is referenced by a
buffer descriptor (BD) that can be anywhere in external memory.
buffer descriptor (BD) that can be anywhere in external memory.
The BD table forms a circular queue with a programmable length. The user can program
the start address of each channel BD table anywhere in memory. See Figure 28-3.
the start address of each channel BD table anywhere in memory. See Figure 28-3.
Bits
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Field
TOD
Ñ
Reset
0000_0000_0000_0000
R/W
R/W
Address
Table 28-3. FCC Transmit-on-Demand Register (TODR)
Table 28-4. TODR Field Descriptions
Field
Name
Description
0
TOD
Transmit on demand
0 Normal
0 Normal
polling.
1 The CP gives high priority to the current TxBD and begins sending the frame does without waiting
for the normal polling time to check TxBD[R]. TOD is cleared automatically.
1Ð15
Ñ
Reserved, should be cleared.