ATM Exceptions
MPC885 PowerQUICC Family Reference Manual, Rev. 2
41-6
Freescale Semiconductor
41.3
Interrupt Queue Mask (IMASK)
IMASK is the interrupt mask for both the receive and transmit sides of a channel and is located in the RCT;
see
Section 37.2.1, “Receive Connection Table (RCT).”
Shown in
Figure 41-5
, it allows the user to enable
or disable interrupt generation. If a bit in IMASK is cleared, the corresponding event does not cause an
entry to be added to the interrupt queue, and the GINT global interrupt counter is not incremented. Note
that the AAL2 bit enables AAL2 functionality for this channel as described in Chapter 42, “AAL2”.
NOTE
Because the masking is performed in microcode, approximately 40 system
clocks must elapse for a change in IMASK to take effect.
15
RXB
Receive buffer. Indicates a buffer has been received. For AAL5, the buffer is not the last buffer in the
frame (indicated by RXF). The RXB interrupt is also generated by other errors that occur when
receiving; in this case, the error condition is reported in the RxBD. This exception is enabled through
the I bit in the RxBD or PTP BD.
16–31 CHNUM
_INDEX
Channel number index. This field represents the CH_CODE of the channel associated with this
interrupt entry or the APC scheduling table base address experiencing overrun.
When not operating in extended channel mode, the CHNUM_INDEX field contains the channel’s
RCT or TCT address in dual-port RAM. In extended channel mode, CHNUM_INDEX is the channel
number.
If the interrupt is an APC overrun (APCO is set), the CHNUM_INDEX field contains the dual-port
RAM offset of the APC priority level experiencing the overrun.
0
1
2
3
4
9
10
11
12
13
14
15
AAL2
—
CNG
—
TQF
UN
RXF
BSY
TXB
RXB
Figure 41-5. Interrupt Queue Mask (IMASK)
Table 41-3. Interrupt Queue Entry Field Descriptions (continued)
Bit
Name
Description
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