SCC Asynchronous HDLC Mode and IrDA
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
25-11
Table 25-10
describes the SCC asynchronous HDLC 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
—
BRK BOF
—
AB
CR
OV
CD
2
Data Length
4
Rx Buffer Pointer
6
Figure 25-7. SCC Asynchronous HDLC RxBDs
Table 25-10. Asynchronous HDLC RxBD Status
and Control Field Descriptions
Bits
Name
Description
0
E
Empty
0 The buffer is full or stops receiving because of an error. The core can read or update any fields
of this RxBD. The CPM cannot reuse this BD while E = 0.
1 The buffer is not full. The CP controls the BD and buffer. The core should not update the BD.
1
—
Reserved, should be cleared.
2
W
Wrap (last 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 incoming data using the BD
pointed to by RBASE. The number of RxBDs in a table is determined by the W bit.
3
I
Interrupt
0 SCCE[RXB] is not set after this buffer is used. SCCE[RXF] is unaffected.
1 SCCE[RXB] or SCCE[RXF] is set when this buffer is used by the asynchronous HDLC
controller.
4
L
Last in frame
0 Not the last buffer in a frame
1 Set by SCC when a buffer is the last in a frame which happens when a closing flag or error is
received. If an error occurs, one or more of the BRK, CD, OV, BOF, CR, and AB bits are set.
The SCC updates RxBD[Data Length].
5
F
First in frame. Set by the SCC when this buffer is the first in a frame.
0 Not the first buffer in a frame
1 First buffer in a frame
6
CM
Continuous mode
0 Normal operation
1 The CP does not clear E after the BD is closed allowing a buffer to be overwritten when the CP
next accesses the BD. However, E is cleared if an error other than CRC occurs during
reception, regardless of CM.
7
—
Reserved, should be cleared.
8
BRK
Break character received. Set when a frame is closed because a break character is received.
9
BOF
Beginning of frame. Set when a frame is closed because a BOF character is received instead of
the expected EOF.
10–11
—
Reserved, should be cleared.
12
AB
Rx abort sequence. Set when an abort sequence or framing error terminates a frame.
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Страница 1172: ...SEC Lite Overview MPC885 PowerQUICC Family Reference Manual Rev 2 46 8 Freescale Semiconductor ...
Страница 1176: ...SEC Lite Address Map MPC885 PowerQUICC Family Reference Manual Rev 2 47 4 Freescale Semiconductor ...
Страница 1214: ...SEC Lite Execution Units MPC885 PowerQUICC Family Reference Manual Rev 2 48 38 Freescale Semiconductor ...
Страница 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Страница 1313: ...MPC885 PowerQUICC Family Reference Manual Rev 2 Freescale Semiconductor B 1 Appendix B Serial Communications Performance TBD ...
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