Nonblocking Mixer

Specifications

Informal

Nonblocking Mixer is a handshake component with three 2-phase handshake ports, two passive and one active. The handshakes on the passive ports are `multiplexed' over the active port. That is, whenever the environment requests on a passive port and the Nonblocking Mixer is not `busy', the Nonblocking Mixer requests on the active port (becoming `busy') and acknowledges on the passive port. When the active port receives an acknowledge, the Nonblocking Mixer becomes 'idle' again.

In contrast to a nr-nonblocking-mixer, the environment of a Nonblocking Mixer need not guarantee mutual exclusion of the passive requests. A request on a passive port while the Nonblocking Mixer is `busy' (waiting for an acknowledge on the active port) is not lost but is handled when the Nonblocking Mixer becomes `idle' again.

When a Nonblocking Mixer receives requests on both passive ports, it will process exactly one of them (and delay the other). The specification leaves the choice open. Often there is a fairness requirement on this choice: if a choice situation arises `infinitely often' then both outputs are chosen `infinitely often'.

XDI

Schematic diagram for a Nonblocking Mixer:

[Zoom|FIG]

Verdect

No information available

DI Algebra

Specification in DI Algebra:

NAME = "Nonblocking-Mixer"
I = { r0, r1, a }
O = { a0, a1, r }

MX = M/a?
M  = a?;[ r0? -> a0!; r!; M, r1? -> a1!; r!; M ]
  
[{r0},{a0}]
[{r1},{a1}]
[{r},{a}]

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