NSCL DAQ Software Documentation
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VMUSB VME access

Name

VMUSB, VMERemote, enumerateVMUSB -- Provide Tcl VME access via VMUSB or control server

Synopsis


package require vmelocal ?1.0?

set deviceInfo [enumerateVMUSB]
set vmusb      [VMUSB name options...]

package require vmeremote ?1.0?
set vmusb      [VMUSBRemote name options...]

$vmusb operation ...

DESCRIPTION

These two packages provide access to simple VME operations via the VM-USB. In addition to the enumerateVMUSB proc, which provides information about the VM-USB controllers attached to the system, the two classes VMUSB and VMUSBRemote provide two highly compatible classes that allow you to perform operations both directly to a VM-USB and remotely via a slow control server running in a VMUSBReadout program.

This package therefore allows you to write slow controls GUIs that can work both without a VMUSBReadout program and with one that does not necessarily have a suitable slow controls driver installed.s

Before we continue with the discussion of the OPTIONS and METHODS each class provides a bit on the enumerateVMUSB proc. This proc returns a list of controller information for each powered up VMUSB controller attached to the local system.

The elements of the list are two element sublists. The first element of each list is the serial number of a VMUSB. The second element of the list is the device handle needed to instantiate a VMUSB object connected directly to that VMUSB.

OPTIONS

The classes provided by these packages have options that must be set at construction time. In addition, there are options shared between the two classes that can affect runtime behavior.

The VMUSB class only requires a -device option at construction time. The value of this option (which once set is readonly) is the device handle used to connect to the selected VM-USB device. Note that if enumerateVMUSB is used to list the VMUSB devices this will be the second element of a sublist that describes one of the devices.

Connection with VMUSBRemote is a bit of a trickier concept and can be dynamically managed. The options needed to specify the actual connection are

-host

The system (IP or DNS name) on which the VMUSBReadout program managing the VMUSB for us is located. If not specified, this defaults to localhost

-port

The TCP/IP port on which the VMUSBReadout's slow control server is listening for connections (specified by its own --port command line option). This defaults to 27000 which is the default used by VMUSBReadout.

-module

The name of the module defined by the control configuration file for the VMUSBReadout program as a vmusb module. See the Module command for more information. The definition of one of these is mandatory.s

In addition to these class specific construction/connection time options both classes share the following options that are used at run-time by applications once connected to a VMUSB or slow controls server:

-amod

The value of this specifies the address modifier used to access the VME bus. The VME bus is divided into a number of orthogonal address spaces that are specified by the number of bits of address used and the privilege mode of the program attempting access.

Most modules don't enforce privilege restrictions. The address modifiers allowed here are therefore simplified to only specify the width of the address bus. Valid values are:

a32

The target module accepts all 32 bits of address. This address space is commonly called extended address space. User mode access is used.

a24

The target module only accepts 24 bits of address. This is commonly called standard address space because initial versions of the VME bus standard did not support 32 bit addressing.

a16

The target module only accepts 16 bits of address. This is commonly called short IO space; because it's intended for use by very simple peripherals that don't have a need for more than 256 bytes of addresssing (the standard only requires a short IO Module to actually decode the top 8 bits of the 16 bit address as a module select).

-persist

This option has no affect on VMUSB object, but is supplied for compatibility to allow scripts that can use either. Used with a VMERemote object, it is a boolean that describes the strategy for managing the TCP/IP connection with the remote control server.

If -persist is a Tcl false value (the default), each operation connects to and then disconnects from the server. This provides maximum reliability (VMUSBReadout can be restarted between operations without the application being aware of that). It also is very inefficiebnt.

If -persist is a Tcl true value, the first operation connects to the server and the connection is maintained until an operation is done with the -persist set to false again. This mode is efficient but not tolerant of exist in the VMUSBreadout.

One approach to the use of -persist that can make sense is a hybrid approach. When many operations need to be done in a short time; first set -persist to true, perform all but the last of those, set -persist to false and then perform the last operation in the sequence. This has the effect of maintaining the connection for the entire sequence of operations and then dropping it after the last operation. This achieves a good compromise between fault tolerance and performance.

METHODS

Both classes have the same methods and parameter signatures. The idea is that the only difference between running a direct connection to the VMUSB and one handled by a VMUSBReadout is which type of object you instantiate.

$object readFirmwareID

Returns the contents of the firmware ID register.

$object vmeRead32 address

Reads the 32 bit at the VME address defined by address. The address modifier used for the operation is determined by the value of the -amod option.

You must know that the target module is capable of 32 bit transfers to use this method.

$object vmeRead16 address

Reads the 16 bit value at the VME address defined by address. The address modifier used for the operation is determined by the value of the -amod option.

You must know the module is capable of performing 16 bit transfers to successfully use this method.

$object vmeRead8 address

Reads the 8 bit value at the VME address defined by address. The address modifier used for the operation is determined by the -amod option.

You must know the module is capable of performing 16 bit transfers to successfully use this methods.

$object vmeWrite32 address data

Writes the 32 bit data parameter to the address. The address modifier is selected by the -amod options. It is your script's responsibility to know that the module can accept a 32 bit write operation at this address.

$object vmeWrite16 address data

Writes the 16 bit data parameter to the address. The address modifier is selected by the -amod options. It is your script's responsibility to know that the module can accept a 16 bit write operation at this address.

$object vmeWrite8 address data

Writes the 8 bit data parameter to the address. The address modifier is selected by the -amod options. It is your script's responsibility to know that the module can accept a 8 bit write operation at this address.

EXAMPLES

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