SCC Transparent Mode
MPC885 PowerQUICC Family Reference Manual, Rev. 2
28-8
Freescale Semiconductor
running the transparent protocol, the other half (receiver or transmitter) can support another protocol. In
such a case, use the PSMR for the non-transparent protocol.
28.9
SCC Transparent Receive Buffer Descriptor (RxBD)
The CPM reports information about the received data for each buffer using an RxBD, closes the current
buffer, generates a maskable interrupt, and starts receiving data into the next buffer after one of the
following occurs:
•
An error is detected.
•
A full receive buffer is detected.
•
An
ENTER
HUNT
MODE
command is Issued.
•
A
CLOSE
RXBD
command is issued.
Table 28-7
describes RxBD status and control fields.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
E
—
W
I
L
F
CM
—
DE
—
NO
—
CR
OV
CD
2
Data Length
4
Rx Buffer Pointer
6
Figure 28-2. SCC Transparent Receive Buffer Descriptor (RxBD)
Table 28-7. SCC Transparent RxBD Status and Control Field Descriptions
Bits
Name
Description
0
E
Empty.
0 The buffer is full or stopped receiving data because an error occurred. The core can read or write
to any fields of this RxBD. The CPM does not use this BD when RxBD[E] is zero.
1 The buffer is not full. This RxBD and buffer are owned by the CPM. Once E is set, the core should
not write any fields of this RxBD.
1
—
Reserved, should be cleared.
2
W
Wrap (final BD in table).
0 Not the last BD in the table.
1 Last BD in the table. After this buffer is used, the CPM receives data into the first BD that RBASE
points to. The number of BDs in this table is determined only by RxBD[W].
3
I
Interrupt.
0 No interrupt is generated after this buffer is used.
1 When this buffer is closed by the transparent controller, the SCCE[RXB] is set. SCCE[RXB] can
cause an interrupt if it is enabled.
4
L
Last in frame. Set by the transparent controller when this buffer is the last in a frame, which occurs
when CD is negated (if GSMR_H[CDP] = 0) or an error is received. If an error is received, one or
more of RxBD[OV, CD, DE] are set. The transparent controller writes the number of frame octets to
the BD’s data length field.
0 Not the last buffer in a frame.
1 Last buffer in a frame.
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Страница 780: ...SCC Ethernet Mode MPC885 PowerQUICC Family Reference Manual Rev 2 27 24 Freescale Semiconductor ...
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