Manual
ibaFOB-D
30
Issue 1.11
“Image generation” area
The information on the right side of the dialog describes the image generation. An im-
age is a collection of bytes that the board writes into the PC system memory via DMA.
This image contains all data of the measured signals on that link.
Here is a short description of the image generation information:
Images processed at interrupt
These counters show how many images were available in the DMA buffer when the
last interrupt fired. This value should normally correspond with the interrupt time di-
vided by the image sampling rate.
Images in DMA buffer
This is the number of images that are in the DMA buffer. This number should remain
constant. If this number starts to increase, the system does not work correctly. This
may happen if e.g. an interrupt is missed.
Images copied to interrupt buffer
This counter shows how many images have been retrieved from the DMA buffer
and have been processed by ibaPDA. This counter should count up continuously.
DMA buffer empty
This counter increments each time the DMA buffer is empty when the interrupt fires.
If this is the case, then the driver sets all signal values of the respective link to 0
(zero). This may happen if the FO link is disconnected.
Time between telegrams
The time interval between the last 2 correctly received telegrams
This is the same value as the time in the FO communication information but the
driver maintains the minimum and maximum values. There shouldn’t be much dif-
ference between the minimum and maximum values.
Image sample rate
The rate at which the board writes images to the DMA buffer. This should be faster
or equal to the fastest time base of the modules connected to this link.
Image size
This is the size of the image in bytes. If you multiply the image size with the image
sample rate then you know how many bytes per second are transferred by this link
over the PCI(e) bus.
Dropped images
This counter increments when the board’s DMA fifo is full and an additional image
arrives. If this happens then something is seriously wrong. This means that the
board is unable to transfer images over the PCI(e) bus.
DMA buffer size
Size of the DMA buffer for this interface.
DMA buffer element size
Size of the elements in the DMA buffer (in bytes).
