
IDT Non-Transparent Switch Operation
PES32NT24xG2 User Manual
14 - 16
January 30, 2013
Notes
Doorbell Registers
Doorbells facilitate event signaling between partitions. Associated with each NT endpoint are one 32-bit
outbound doorbell register and one 32-bit inbound doorbell register. An outbound doorbell request from an
NT endpoint is initiated by writing a one to the corresponding bit in the Outbound Doorbell Set (OUTD-
BELLSET) register.
–
Outbound doorbell requests are edge-triggered, meaning that the action of writing a one to a bit
in the OUTDBELLSET register causes the corresponding outbound doorbell to be signaled.
Writing a zero to any bit in the OUTDBELLSET register has no effect on the doorbell request.
Reading from the OUTDBELLSET register always returns 0x0.
An inbound doorbell request to the NT endpoint results in the setting of the corresponding bit in the
Inbound Doorbell Status (INDBELLSTS) register.
–
The setting of a bit in the INDBELLSTS register may be used to generate an NT endpoint interrupt.
–
Individual bits in the INDBELLSTS register may be masked from generating an interrupt by setting
the corresponding bit in the Inbound Doorbell Mask (INDBELLMSK) register.
The logical operation of doorbells is illustrated in Figure 14.9.
For each of the 32 outbound doorbell request, the requests from all partitions are logically OR-ed
together to form a global doorbell request. This global doorbell request is then used to initiate inbound door-
bell requests to each of the partitions.
An outbound doorbell may initiate inbound doorbell requests in one or more partitions. All inbound door-
bell requests share the same index. In other words, writing a one to bit position 8 in the OUTDBELLSET
register may initiate an inbound doorbell request in multiple partitions, but each inbound doorbell request
will be associated with the same bit position (e.g., position 8) as that of the outbound request.
Associated with each outbound doorbell is a Global Outbound Doorbell Mask (GODBELLMSKx) register
that contains a bit corresponding to each partition. When a bit in this register is set, outbound doorbell
requests from the corresponding partition are masked. For example, setting bit 7 in the GODBELLMSK4
register masks doorbell 4 requests from partition 7.
–
When a doorbell request from a partition is masked, the state of the doorbell in the corresponding
partition plays no role in determining the state of the global doorbell status.
A global doorbell request results in the initiation of corresponding inbound doorbell requests to all
unmasked partitions.
–
A global doorbell request may be masked to a partition by setting the corresponding partition bit
in the Global Inbound Doorbell Mask (GIDBELLMSKx) register.
–
When an inbound doorbell request is masked to a partition, the state of the global doorbell status
plays no role in determining the state of the corresponding inbound doorbell request in that parti-
tion.
Содержание PCI Express 89HPES32NT24xG2
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