80KSBR200 Datasheet, PDF (33/172 Pages) Integrated Device Technology – sRIO SERIAL BUFFER FLOW-CONTROL DEVICE

IDT 80KSBR200
Notes
Advanced Datasheet*
5.0 Doorbells and Interrupts
Interrupt pins and packetized Doorbells are used to pass interrupts and messages out of the SerB. Outgoing doorbell
packets and interrupts are generated by flags.
A flag is considered any event that results in a bit being stored in the "flag register". The content and masks for the flag
registers are detailed in Flag and Flag Mask Register section. Events at these locations will cause a flag to be stored at
the designated location within the flag register as they occur.
In addition to simply residing within the flag register, any flag may cause an interrupt, notifying external devices that a
flag event has occurred. This interrupt is considered a "doorbell" and may be issued in one of the following ways:
◆ _{External output pin toggling (two pins, each with a mask).}
◆ _{sRIO Type 10 packets sent over S-Port.}
Each flag register has four mask registers designating which flags should cause the associated "doorbell" or interrupt
on the port. A violation of any unmasked flag shall cause the designated interrupt to occur. Of the four mask registers,
Mask 1 is associated with S-Port and will cause doorbells to be sent. Mask 3 and Mask 4 are not associated with a port
and will cause external interrupt pin 0 and interrupt pin 1o toggle respectively. Mask 2 is reserved for future use.
As a default, the flag register mask will not generate any interrupts (full mask). Interrupt generation must be
programmed by the mask registers.
In the event that multiple flags toggle, the interrupts/doorbells will be generated based upon the priority programmed in
the flag registers. In the event that flags have the same priority, the flags will be handled in the order they occurred. In the
event that multiple flags with the same priority toggle simultaneously, the flag with lowest address will have priority over
flags with higher addresses.
5.1 Doorbell Characteristics
When a flag causes a doorbell, the doorbell includes the following:
◆ _{The register number containing the toggled flag}
◆ _{The flag number within the register that toggled}
◆ _{The entire unmasked content of the flag register (flags only)}
sRIO doorbells are limited to a 16-bit payload.
5.1.1 sRIO Flag Doorbell Packet
An 8-bit sRIO doorbell packet is shown in Figure 10. The Target ID of the sRIO doorbell is programmed into the flag
register causing the doorbell. The Source ID will be the source ID of the doorbell in the SerB. If the doorbell is generated by
a queue, the destination ID associated with the queue will be the source ID for the doorbell. If the doorbell is generated by
something other than a queue (e.g. a link error), the sRIO generated destination ID of the SerB shall be used as the source
ID of the doorbell.
Figure 10 sRIO Doorbell Packet
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March 19, 2007
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