The VMUSB readout framework provides support for the Wiener-JTec VM-USB VME controller. The VM-USB is a USB VME controller that uses a Xilinx gate array to implement a VME list processor. This allows events to be readout autonomously by the VM-USB without intervention by the host processor. The VMUSB Readout framework provides:
A high level approach to the problem of data taking with the VM-USB
Support for user written device support without any need to understand the format of list operations supported by the VM-USB. Drivers can be written in C++.
Direct insertion of data taken to an arbitrary destination ringbuffer.
A potential data source for the NSCL event builder.
This chapter provides:
The philosophy behind the VMUSB readout framework.
How to write configuration files for the VMUSB readout framework.
How to write device support modules in in C++ and incorpoprate those modules into the VMUSB readout framework.
How to write device support modules in Tcl and incorporate those modules into a VM-USB readout DAQ configuration file.
How to write device support modules for the slow control server in C++
How to write device support modules for the slow control server in Tcl.
The slow controls protocol and its primitives.
Variable monitoring.
Information on how to run VMUSBReadout under the state/boot managers that were introduced with NSCLDAQ-11.0
Reference information is available in the 3vmusb section of the reference material.
The VM-USB readout framework taks a high level approach to specifying and configuring a readout case. Users write a configuration file that specifies at a very high level which devices are used, their configuration and which ones need to be read under which circumstances (The VM-USB supports up to 8 lists with differing trigger conditions).
The framework supports data taking (physics and scaler triggers), as well as a mechanism for building and integrating control panels for slow controls devices. A plugin architecture supports the addition of user support for devices that are not now supported by internal drivers.
The recurring concepts for configuring data taking and slow controls devices are:
A Tcl configuration file describes the devices used by the experiment.
Each supported device class is represented in the configuration file by a Tcl command ensemble. The command ensemble provides subcommands that allow you to create, configure and query the configuration of physical devices (device instances).
The device configuration is represented in the configuration file in manner analagous to the state of a Tk widget. That is, you never actually program the device directly, you simply specify the desired configuration. The actual programming is done by the device class's device support software.
In accordance with the way the VM-USB operates, you can create 8 lists or stacks in VM-USB parlance. Some of these stacks have special meaning to either the framework or to the VM-USB. One stack is reserved by the VM-USB as the target of periodic triggers and is used to support scaler readout/display. A second stack is reserved for a software periodic trigger and is used to support devices that require periodic monitoring (e.g. detector bias supplies which may trip during operation due to interlock conditions). Of the remaining 6 stacks one can be triggered by a VM-USB front panel input and the remaining 5 can be triggered by VME backplane interrupts.
Each stack has, configuration properties as well. One configuration property is the set of modules managed by that stack. Modules managed by that stack are initialized by the software, in accordance with their configuration, and contribute to the readout list that executes in response to that stack's trigger.