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Chapter 6 NI-VXI Configuration Utility
VXI/VME-PCI8022 for Solaris 6-16
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National Instruments Corporation
Caution: Do not configure more than one MXIbus device to drive MXIbus CLK10.
Having a second device driving MXIbus CLK10 could damage the device.
MXI Transfer Limit
Use this feature to control how many data transfers the PCI-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 256, 64, and 16 transfers. If
you do not want the PCI-MXI-2 to hold the MXIbus for an unlimited
period of time, you can use this control to select one of these values.
Synchronous MXI
The MXIbus has a special high-speed block protocol for transferring
large blocks of data. This protocol, SYNC-MXI, locks the MXIbus
during the transfer, which prevents anyone else from using the bus.
VXImove() uses this protocol to transfer data.
If a VXI interrupt or signal comes in while a synchronous MXI move is
underway, there can be a problem. Using the SYNC-MXI protocol will
prohibit access to the MXI bus, which will prevent you from responding
to an interrupt, and prevent bus monitoring devices from accessing the
bus at regular intervals.
By default this option is enabled—the VXImove uses Synchronous
MXI checkbox is checked. You can also disable SYNC-MXI
programmatically in
VXImove(). However, if you have an older
NI-VXI application that does not disable SYNC-MXI
programmatically, you can deselect the checkbox to force your
application to not use SYNC-MXI, if necessary.
MXI-2 Auto Retry
The PCI-MXI-2 has an automatic retry feature for cycles that map from
the MXI bus to the PCI bus. By default this option is enabled—the
Enable MXI-2 Auto Retry checkbox is checked.
Normally, when a cycle maps from the MXI bus to the PCI bus, any
retry response received on the PCI bus is passed to the MXI bus. When
the MXI-2 auto retry feature is enabled, the PCI-MXI-2 automatically
retries any PCI cycle when the PCI host responds to a cycle with a retry.
The PCI-MXI-2 automatically continues to retry the PCI cycle until it
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