Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 987

CT Offset Bits
0x00 8
(cont.)
9
10 CNG/NCRC CNG—Congestion (AAL5 only). Used internally by the CP, RCT[CNG] indicates
11
12 CNGI/PTP
Freescale Semiconductor
Table 37-3. RCT Field Descriptions (continued)
Name
HEC Header error control indication (serial ATM only). Used internally by the CP,
RCT[HEC] indicates that a HEC error has been detected in at least one cell of the
current frame.
For AAL5, this bit is set as soon as a cell of the current frame is determined to
have a HEC error. At the end of the frame, this bit is copied to the last RxBD[HEC]
of the frame. For AAL0, this bit is copied to the RxBD[HEC] for each cell.
0 No HEC error has been detected.
1 A HEC error has been detected.
CLP Cell loss priority indication (AAL5 only). Used internally by the CP, RCT[CLP]
indicates that at least one low priority cell has arrived as part of the current AAL5
frame. This bit is set as soon as a cell of the current frame is determined to have
a CLP bit set in its header. At the end of the frame, this bit is copied to the last
RxBD[CLP] of the frame. For AAL0 channels, the CLP indication is available in
the cell header in the data buffer.
0 No low priority cells have arrived in the current frame.
1 A low priority cell has arrived during the current frame.
that congestion has been reported in the last cell of the current frame. RCT[CNG]
is set only if the last cell of the current AAL5 frame has arrived with the PTI[EFCI]
bit set in its header. At the end of the frame, this bit is copied to the last
RxBD[CNG] of the frame.
0 No congestion has been reported.
1 Congestion has been reported.
NCRC—No CRC (AAL0 only). NCRC is used to disable CRC10 calculations. If
CRC10 is not required for this channel, set this bit to gain better CPM utilization.
0 Perform CRC10 calculations.
1 Disable CRC10 calculations.
INF In frame. The receiver sets RCT[INF] when a new frame starts and clears it when
the frame ends. This bit is used internally.
0 Idle state. No buffer is open for this channel.
1 Receiving. The receiver is in the middle of a frame; a receive buffer is open.
CNGI (AAL5 only)- Congestion interrupt. This bit enables interrupts when the
SAR layer detects a cell's PTI[EFCI] bit is set.
0 Disable congestion interrupts. Congestion is indicated in the last RxBD[CNG]
of the frame.
1 Enable congestion interrupts. An interrupt entry is added to the interrupt queue
if PTI[EFCI] is set in a received cell. See
PTP (AAL0 only). Port-to-port cell switching. Setting this bit turns a regular RCT
into a PTP RCT, so it should be cleared in this context.
0 Normal AAL0 mode.
1 Activate the port-to-port switching mechanism. See
"Port-to-Port Protocol-Specific RCT."
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Buffer Descriptors and Connection Tables
Description
Chapter 41, "ATM Exceptions."
Section 37.2.1.1,
37-13