Chapter 6 NI-VXI Configuration Utility
© National Instruments Corporation 6-27 PCI-MXI-2 for Linux

Arbiter Timeout

An arbitration timeout feature is available on the VXI/VME-MXI-2 when
it is acting as the VMEbus arbiter. This feature applies only to a VXI Slot 0
(VMEbus System Controller) VXI/VME-MXI-2. By default, this option is
enabled.
The timer begins when the arbiter circuit on the VXI/VME-MXI-2 drives
one of the BGOUT lines on the backplane. If no device takes over the bus
within the timeout limit, the BGOUT is removed and the bus is either idle
or granted to another requester.
MXI Bus Options
Use the options in this group to control features of the MXIbus interface on
the VXI/VME-MXI-2 module.
MXI Bus System Controller
You can use the System Controller control to determine whether the
VXI/VME-MXI-2 acts as the MXI Bus System Controller. When the Auto
setting (the default setting) is active, the VXI/VME-MXI-2 automatically
can sense from the MXIbus cable whether it should be the controller.
You can select either Yes or No to manually determine if the
VXI/VME-MXI-2 should be the MXI Bus System Controller. You must
still be certain to cable the MXIbus system appropriately when you make
either of these selections.
MXI Bus Timeout Value
The MXI Bus Timeout (BTO) is a watchdog timer for transfers on
theMX Ibus. The MXIbus BTO unit operates only when the
VXI/VME-MXI-2 is acting as the MXI Bus System Controller. The
functionality of this control is similar to that of the VXI Bus Timeout
control described in the VXI/VME Bus Options section. Theoptions range
from 8µs to 128 ms, w ith a default value of 1 ms.
After the specified amount of time has elapsed, the BTO circuitry
terminates a MXIbus cycle if no slave has responded. The BTO circuitry is
automatically deactivated when the VXI/VME-MXI-2 is notacting as the
MXI Bus System Controller. The BTO is also disabled when the current
MXIbus cycle maps to the VXI/VMEbus through a VXI/VME-MXI-2.