Controller#
The controller’s purpose is to interface an ONI hardware system with the host computer. It aggregates and routes device data and provides transparent access to all devices irrespective of their physical location or physical means of communication between devices and controller.
Acquisition Counter#
The controller MUST have access to a high-resolution, monotonic counter
(typically driven by a high-resolution crystal oscillator, resonator, PLL,
etc.). This counter is used to synchronize data from all devices independently
of their origin hub. The controller MUST capture the counter value when
receiving a sample and use that value for the acqclk_cnt
field of the corresponding frame.
Note
The controller captures the acquisition counter when it receives a
sample and uses its value for acqclk_cnt field of the corresponding
frame.However, due to hub to controller transmission delays,
this time may have an offset from the time of sample creation. To account
for this, hubs contain a register indicating the
measured transmission latency. Users can use this value to more precisely
synchronize samples between hubs.
Hard Reset#
A controller MUST implement a hard reset that restores both it and its dependent hardware elements (hubs and devices) to a power-on configuration state. This signal MUST be issued through an Out Of Band (OOB) mechanism, triggered by the Driver Translator, and MUST NOT rely on the Controller Communication Channels.
The Driver Translator SHOULD issue a hard reset when communication between the host and controller is initially established and when it ends, either normally or exceptionally.
Note
The hard reset signal is not to be confused with the system soft reset. A hard reset returns all elements in the hardware hierarchy governed by a given controller to their to their power on state but does not trigger a device map transmission. A soft reset might may preserve the values of some registers and configurations (as documented on in this specification or a Device Datasheet) and always triggers a device map transmission to the host.
Hardware-Specific Parameters#
Different ONI-compliant controller implementations might specify hardware-specific parameters related to standard ONI elements. These need to be informed through a specific address space reserved for ONI compliance parameters. Driver translators can use this information to hide hardware-specific details to the relevant API.
Optional Features#
The specification includes features that MAY or MAY NOT be implemented in controller hardware. The ONI compliance address space includes registers to determine the availability of each optional feature and its parameters, if applicable.