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CAEN VME Bridges
Introduction
CAEN offers two different versions of their VME bridge. One with
an optical link, and a second with a USB interface:
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The CAEN optical bridge. It consists of following modules:
- A2718 : The VME Controller.
- A2818 : The PCI card.
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The CAEN USB bridge (ref. No. A1718). This module is software compatible with the
optical version, but needs a different driver.
Link to the CAEN pages:
http://www.caen.it/nuclear/product.php?mod=V2718
Some technical information:
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The VME controllers of the optical version can be chained (i.e. one
PCI interface can control several crates which are connected by and
optical link in a ring topology.)
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The maximal length of the fiber is specified by the producer of the optical
link components to be 275m for a fiber of type 62.5/125um. (This is the fiber
type which comes with the module from CAEN). When you use the fiber type 50/125um
the link producer claims that the maximal link length is 550m.
Attention: Both maximal lengthes have not been tested by anybody so far.
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The PCI board A2818 supports 3V and 5V slots PC slots.
Attention: There is a jumper on the
card which must be set correctly!
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The software consists of a drivers (specific for the optical or the
USB version) and of a user library which is identical for both versions.
This means that the user code which works with one module automatically
also works with the other version. An exception to this might be software
which need a handling of interrupts. Since the USB technology is not
adequate for real time applications, interrupt handling in the USB
version of the VME bridge is reduced to a simple polling mechanism:
The user has to poll the controller if on the VME side an interrupt
has occured.
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The optical version supports full interrupt handling which means
that VME interrupts are routed through the bridge and generate an
interrupt on the PCI bus. How in detail this interrupt is handled
by the software is described in the section "Status".
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