MSC8144E Reference Manual, Rev. 3
16-80
Freescale
Semiconductor
Serial RapidIO
®
Controller
16.4.2
Doorbell Controller
The RapidIO architecture specification defines a doorbell type with no data payload that is
transferred using inbound and outbound doorbell controllers. The MSC8144E RapidIO
interconnect doorbell unit supports both inbound and outbound doorbells. The doorbell entry size
is fixed at 64 bits because doorbell packets only pass a small amount of information, making the
enqueue and dequeue pointers double-word addresses.
Inbound doorbells are handled by the doorbell controller similar to the way the message
controller handles inbound data messages. The doorbell controller receives the doorbells and
places them in a circular queue located in local memory. Additional doorbells can be received
and forwarded to memory before the previous doorbell memory write completes as long as the
RapidIO priority is the same or lower than the previous doorbell. The doorbell is retried if the
RapidIO priority is higher than the previous doorbell.
Table 16-12 depicts an example of the structure of the inbound doorbell queue and pointers. The
doorbell queue has eight entries, three of which are currently valid. The doorbell controller
enqueues doorbells and the local processor dequeues doorbells.Each inbound doorbell controller
has a dedicated interrupt to notify software that there are incoming doorbells.
Outbound doorbells are generated through a memory-mapped write port rather than a queue. An
outbound doorbell must complete before another outbound doorbell can be generated. The
outbound doorbell controller has a dedicated interrupt used to notify software that a doorbell was
sent.
Figure 16-12. Inbound Doorbell Queue and Pointer Structure
Doorbell
Entry
Doorbell
Entry
Doorbell
Entry
Enqueue Pointer
Dequeue Pointer
Dequeue Pointer
Local Processor Read
Inbound
Doorbell
Controller
Local Memory
Packets from
RapidIO interface
Содержание MSC8144E
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Страница 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Страница 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Страница 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Страница 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
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