Chapter 3
VXI Configuration Utility
3-18
ni.com
Notice that the VXI/VME-MXI-2 has a limit on the number of automatic
retries it will perform on any one cycle. If the limit is exceeded and the
VXI/VME-MXI-2 receives another retry, it will pass a retry back to the
MXIbus even though
VXI Auto Retry
is enabled.
MXI Bus Timeout Value
The MXIbus Bus Timeout (BTO) is a watchdog timer for transfers on the
MXIbus. The MXIbus BTO unit operates only when the VXI/VME-MXI-2
is acting as the MXIbus System Controller. The functionality of this feature
is similar to that of the
VXI Bus Timeout
feature described previously.
The options range from 8
µ
s to 128 ms, with 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 not acting as the
MXIbus System Controller. The BTO is also disabled when the current
MXIbus cycle maps to the VXI/VMEbus through a VXI/VME-MXI-2.
Transfer Limit
You can use this feature to control how many data transfers the
VXI/VME-MXI-2 will perform on the MXIbus before releasing it to
another master device that is requesting use of the bus. The default setting
holds the MXIbus for an unlimited period of time.
The other options you can choose from are 16, 64, and 256 transfers. If you
do not want the VXI/VME-MXI-2 to hold the MXIbus for an unlimited
period of time, you can select one of these values.
MXI CLK10 Signal
The VXI-MXI-2 can either receive or drive the MXIbus CLK10 signal.
In its default setting, the VXI-MXI-2 uses the switch setting of S7 to
determine the signal direction.
♦
VME Users
—This option is
not
applicable to the VME-MXI-2.
You can use the
Drive
or
Receive
options to override the setting of S7
and control the direction of the MXIbus CLK10 signal. If you set the
VXI-MXI-2 to receive the MXIbus CLK10 signal, configure the W3
jumper setting to use the MXIbus as the source for generating the VXIbus
CLK10 (applicable only if the VXI-MXI-2 is a Slot 0 device). When you
set the VXI-MXI-2 to drive the MXIbus CLK10, it uses the VXIbus CLK10