Parallel Interface Port (PIP)
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
33-13
33.5.2
The PIP Rx Buffer Descriptor (RxBD)
Using buffer descriptors, the CP confirms 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 field. The data length and buffer pointer are
described in
Section 33.5, “PIP Buffer Descriptors,”
above.
2
W
Wrap (last buffer descriptor in TxBD table). The number of TxBDs in the table is determined only by
the W bit and space constraints of the dual-port RAM.
0 Not the last descriptor in the TxBD table.
1 The last BD in the TxBD table. After this BD is processed, the current TxBD pointer wraps to the
top of the TxBD table (TBASE).
3
I
Interrupt
0 No interrupt is generated after this buffer is serviced.
1 PIPE[TXB] is set when this buffer is serviced by the CP, which can cause an interrupt.
4
L
Last
0 Not the last buffer of the frame.
1 Last buffer of the frame.
5
—
Reserved and should be cleared.
6
CM
Continuous mode
0 Normal operation
1 The CP does not clear R after this buffer is closed, allowing the associated buffer to be resent
when the CP next accesses this BD. However, R is cleared if an error occurs during transmission.
7–11
—
Reserved, should be cleared.
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
—
Reserved, should be cleared.
Bit
0
1
2
3
4
5
6
7
8
15
0
E
—
W
I
C
—
CM
SL
—
2
Data Length
4
Rx Buffer Pointer
6
Figure 33-10. PIP Rx Buffer Descriptor (RxBD)
Table 33-9. PIP TxBD Status and Control Field Descriptions (continued)
Bits
Name Description
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