4.1.4.1 Queue N Register A (0x00000000 + 16×N)
The Queue N Register A (Figure 4-11) provides an entry count feature, which is a count of the number of descriptors currently contained in the queue.
Figure 4-11 Queue N Register A (0x00000000 + 16×N)
Reserved |
QUEUE_ENTRY_COUNT |
Legend: R = Read only; - n = value after reset |
Table 4-14 Queue N Register A Field Descriptions
Bit |
Field |
Description |
31-19 |
Reserved |
Reads return 0 and writes have no effect. |
18-0 |
QUEUE_ENTRY_COUNT |
This field indicates how many packets (descriptors) are currently queued on the queue. This count is incremented by 1 whenever a packet is added to the queue. This count is decremented by 1 whenever a packet is popped from the queue. Do not read this register unless you also intend on popping the queue with Reg D. To obtain the descriptor count without also popping the queue, use Queue N Status and Configuration Reg A in the Queue Peek region. |