MOTOROLA
Chapter 33. Parallel Interface Port
33-13
Part V. The Communications Processor Module
33.5.2 The PIP Rx Buffer Descriptor (RxBD)
Using buffer descriptors, the CP conÞrms reception or indicates error conditions so the core
knows which buffers have been serviced. Figure 33-10 shows the PIP RxBD.
Table 33-10 describes the PIP RxBD status and control Þeld. The data length and buffer
pointer are described in Section 33.5, ÒPIP Buffer Descriptors,Ó above.
12
F
Fault.
0 The FAULT status line has remained negated during transmission.
1 The FAULT status line has been asserted during transmission.
13
PE
Paper error.
0 The PERROR status line has remained negated during transmission.
1 The PERROR status line has been asserted during transmission.
14
S
Select error.
0 The SELECT status line has remained asserted during transmission.
1 The SELECT status line has been negated during transmission.
15
Ñ
Reserved and should be cleared.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
E
Ñ
W
I
C
Ñ
CM
SL
Ñ
2
Data Length
4
Rx Buffer Pointer
6
Figure 33-10. PIP Rx Buffer Descriptor (RxBD)
Table 33-10. PIP RxBD Status and Control Field Descriptions
Bits
Name Description
0
E
Empty.
0 The buffer associated with this descriptor is full or stopped receiving data because an error occurred.
The core can read or write any Þelds of this RxBD. The CP cannot use this BD while E is 0.
1 The buffer associated with this BD is empty or is receiving data. Once E is set, the core should not
write any Þelds of this RxBD.
1
Ñ
Reserved and should be cleared.
2
W
Wrap (last buffer descriptor in RxBD table). The number of RxBDs in the table is determined only by the
W bit and space constraints of the dual-port RAM.
0Not the last BD in the RxBD table.
1 The last BD in the RxBD table. After this BD is processed, the current RxBD pointer wraps to the top
of the RxBD table (RBASE).
3
I
Interrupt.
0 No interrupt is generated after this buffer is Þlled.
1 PIPE[RXB] is set when the CP Þlls this buffer, signaling the core to process the buffer. The RXB bit
causes an interrupt if not masked.
Table 33-9. PIP TxBD Status and Control Field Descriptions (Continued)
Bits
Name Description
Содержание MPC860 PowerQUICC
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