Synchronous is not really a protocol but a concept. At its core, it refers to serial data, strobed in by a separate clock signal.
•The data is sampled on one or both of the clock edges.
•There are no predefined number of bits per field (symbol) or fields per frame.
•There are no predefined framing indicators. The field lengths usually vary within a frame and are often data dependent.
There are many link-level implementations of serial protocols and many higher levels of protocols built on top of them.
The pre-processor honors the select signal (ignores clocks while disabled/deselected) but ignores the FrameSYNC and Field signals. If the user enables either of these, the pre-processor simply detects transitions on the selected lines and reports them to the plug-in.
Configuration Options provided by the pre-processor
Selects which physical channel to assign to the CLOCK
Selects which physical channel to assign to the DATA bus
Selects which physical channel to assign to the ENABLE.
The enable can be disabled if not used
Selects which physical channel to assign to the FRAME SYNC.
This can be used to identify frame limits
The FRAME SYNC can be disabled if not used.
Selects which physical channel to assign to the FIELD SYNC.
This can be used to identify field limits
The FIELD SYNC can be disabled if not used.
Selects which edge of the clock to use to strobe in data
Selects the active level for the Select signal
This pre-processor can generate more than 1 event at a time. It sets 1 or more event flags in data byte to indicate which events occurred at this timestamp. It also updates some status bits in that same byte to indicate the current state of some of the control signals. The event flags and status levels are defined below:
DATAEVENT FLAG (bit 7 : 0x80)
When this bit is set, state data was strobed in at this time. The data field holds the clocked data.
SELECTEVENT FLAG (bit 6 : 0x40)
When this is set, the SELECT channel transitioned. The SELECTSTATE tells us if it went active or inactive
FrameSYNCEVENT FLAG (bit 5 : 0x20)
When this is set, the FrameSYNC channel transitioned. The Frame SYNCLEVEL tells us the new level
Field SYNCEVENT FLAG (bit 4 : 0x10)
When this is set, the FieldSYNC channel transitioned. The Field SYNCLEVEL tells us the new level
SELECTSTATE (bit 2 : 0x04)
The current state of the select signal. 1 => enabled, 0=> disabled (regardless of the logic level on the physical channel)
Frame SYNCLEVEL (bit 1 : 0x02)
The current logic level of the FrameSYNC channel. The preparser assumes nothing about the meaning of this signal so it passes the actual logic level to you
Field SYNCLEVEL (bit 0 : 0x01)
The current logic level of the FieldSYNC channel. The preparser assumes nothing about the meaning of this signal so it passes the actual logic level to you