Xtium-CLHS PX8 User's Manual Xtium-CLHS PX8 Reference
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Transfer Events
Transfer events are the ones related to the transfer module. Transfer events provide feedback on
image transfer from onboard memory frame buffers to PC memory frame buffers.
• Start of Frame
Start of Frame event generated when the first image pixel is transferred from on-board
memory into PC memory.
The Sapera event value is CORXFER_VAL_EVENT_TYPE_START_OF_FRAME.
• End of Frame
End of Frame event generated when the last image pixel is transferred from on-board
memory into PC memory.
The Sapera event value is CORXFER_VAL_EVENT_TYPE_END_OF_FRAME.
• End of Transfer
End of Transfer event generated at the completion of the last image transfer from on-board
memory into PC memory. Issue a stop command to the transfer module to complete a
transfer (if transfers are already in progress). If a frame transfer of a fixed number of
images is requested, the transfer module will stop transfer automatically. The Sapera event
value is CORXFER_VAL_EVENT_TYPE_END_OF_TRANSFER.
Trigger Signal Validity
The ACU ignores external trigger signal noise with its programmable debounce control. Program
the debounce parameter for the minimum pulse duration considered as a valid external trigger
pulse. For more information see Note 1: General Inputs / External Trigger Inputs Specifications.
Supported Transfer Cycling Methods
The Xtium-CLHS PX8 supports the following transfer modes, which are either synchronous or
asynchronous. Note that the Xtium does not make any use of the trash buffer. Images are
accumulated in on-board memory in a FIFO type manner. When no memory is available for a new
image to be stored, the image is discarded and the CORACQ_VAL_EVENT_TYPE_FRAME_LOST is
generated. On-board memory can get filled up if the rate at which the images are acquired is
greater than the rate at which the DMA engine can write them to host buffer memory. On-board
memory can also get filled-up if there are no more empty buffers available to transfer the on-board
images.
When stopping the image acquisition, the event CORXFER_VAL_EVENT_TYPE_END_OF_TRANSFER
will occur once all images currently in the on-board memory are transferred to host buffer memory.
Note that if the application does not provide enough empty buffers, the Xtium event will not occur
and an acquisition abort will be required.
• CORXFER_VAL_CYCLE_MODE_SYNCHRONOUS_WITH_TRASH
Before cycling to the next buffer in the list, the transfer device will check the next buffer's
state. If its state is full, the transfer will keep the image in on-board memory until the next
buffer’s state changes to empty. If the on-board memory gets filled, frame lost events will
be generated.
• CORXFER_VAL_CYCLE_MODE_SYNCHRONOUS_NEXT_EMPTY_WITH_TRASH
When starting an acquisition, the buffer list is put in an empty buffer queue list in the exact
order they were added to the transfer. Whenever a user sets a buffer to empty, it is added
to the empty buffer queue list, so that after cycling once through the original buffer list, the
buffers acquired into will follow the order in which they are put empty by the user. So in this
mode, the on-board images will be transferred to host buffer memory as long as there are
buffers in the empty buffer queue list. If the on-board memory gets filled, the frame lost
event will start occurring.
• CORXFER_VAL_CYCLE_MODE_ASYNCHRONOUS
The transfer device cycles through all buffers in the list without concern about the buffer
state.
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