GR712RC-UM, Jun 2017, Version 2.9 207 www.cobham.com/gaisler
GR712RC
27.4.4 Virtual Channel Multiplexing
The Virtual Channel Multiplexing Function is used to multiplex Transfer Frames of different Virtual
Channels of a Master Channel. Virtual Channel Multiplexing in the core is performed between two
sources: Transfer Frames provided through the Virtual Channel Frame Service and Idle Frames. Note
that multiplexing between different Virtual Channels is assumed to be done as part of the Virtual
Channel Frame Service outside the core.
The Virtual Channel Frame Service user interface is described above. The Idle Frame generation is
described hereafter.
Idle Frame generation can be enabled and disabled by means of a register. The Spacecraft ID to be
used for Idle Frames is programmable by means of a register. The Virtual Channel ID to be used for
Idle Frames is programmable by means of a register.
Master Channel Counter generation for Idle Frames can be enabled and disabled by means of a regis-
ter (only for TM). Note that it is also possible to generate the Master Channel Counter field as part of
the Master Channel Generation function described in the next section. When Master Channel Counter
generation is enabled for Idle Frames, then the generation in the Master Channel Generation function
is bypassed.
The Virtual Channel Counter generation for Idle Frames is always enabled (both for TM and AOS)
and generated in the Virtual Channel Generation function described above.
Extended Virtual Channel Counter generation for Idle Frames can be enabled and disabled by means
of a register (only for TM, as defined for ECSS and PSS). This includes the complete Transfer Frame
Secondary Header.
Virtual Channel Counter Cycle generation for Idle Frames can be enabled and disabled by means of a
register (only for AOS).
If Frame Secondary Header generation is not supported.
If Operation Control Field generation is enabled in the Master Channel Generation function described
in the next section, it can be bypassed for Idle Frames, programmable by means of a register. This
allows VC_OCF or MC_OCF realization.
27.4.5 Master Channel Generation
The Master Channel Counter can be generated for all frames on a master channel (only for TM). It can
be can be enabled and disabled by means of a register. The generation can also be bypassed for Idle
Frames or Transfer Frames provided via the DMA interface.
The Frame Secondary Header (FSH) is not supported.
The Operational Control Field (OCF) can be generated from a 32-bit register. This can be done for all
frames on an master channel (MC_OCF) or be bypassed for Idle Frames or Transfer Frames provided
via the DMA interface, effectively implementing OCF on a per virtual channel basis (VC_OCF).
27.4.6 Master Channel Frame Service
The Master Channel Frame Service user interface is equivalent to the previously described Virtual
Channel Frame Service user interface, using the same DMA interface. The interface can thus be used
for inserting both Master Channel Transfer Frame and Virtual Channel Transfer Frames.
27.4.7 Master Channel Multiplexing
The Master Channel Multiplexing Function is used to multiplex Transfer Frames of different Master
Channels of a Physical Channel. Master Channel Multiplexing is performed between three sources:
Master Channel Generation Service, Master Channel Frame Service and Idle Frames.
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