Rainbow Electronics DS3134 - Manual (Page 112)

DS3134
112 of 203
The Receive Done Queue is circular queue. To keep track of the addresses of the circular queue in the
Receive Done Queue, there are a set of internal addresses within the device that accessed by both the Host
and the DMA. On initialization, the Host will configure all of the registers shown in Table 8.1.4A. After
initialization, the DMA will only write to (i.e. change) the write pointer and the Host will only write to the
read pointer.
Empty Case
The Receive Done Queue is considered empty when the read and write pointers are identical.
Receive Done Queue Empty State
empty descriptor
empty descriptor
empty descriptor
read pointer > empty descriptor < write pointer
empty descriptor
empty descriptor
empty descriptor
Full Case
The Receive Done Queue is considered full when the read pointer is ahead of the write pointer by one
descriptor. Hence, one descriptor must always remain empty.
Receive Done Queue Full State
valid descriptor
valid descriptor
empty descriptor < write pointer
read pointer > valid descriptor
valid descriptor
valid descriptor
valid descriptor