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Configuration and Installation Chapter 3
VXI-MXI User Manual 3-16 © National Instruments Corporation
MXIbus System Controller Timeout
The MXIbus System Controller is also responsible for the MXIbus system timeout. The timeout
period begins when a MXIbus data strobe (DS) is received. The period stops when a MXIbus
DTACK or BERR is detected. If a timeout occurs, the MXIbus System Controller sends a
MXIbus BERR to clear the MXIbus system. On power up, this timeout is between 100 µs and
400 µs as configured by the MXI Controller BTO Level jumper array (refer to Figure 3-1 for its
location). You can extend the timeout to a value between 100 ms and 400 ms by setting the
LNGMXSCTO bit in the MXIbus Control Register. It is best to have a long MXIbus System
Controller timeout in MXIbus systems with many devices or in situations where one or more
MXIbus devices use a large amount of MXIbus bandwidth.
Figure 3-13 shows how to position the jumper array to set the MXIbus System Controller
timeout value. When the VXI-MXI is not configured to be the MXIbus System Controller, the
setting of this jumper array has no effect. Notice that when the LNGMXSCTO bit in the
MXIbus Control Register is zero, the selected timeout value is in microseconds. When the
LNGMXSCTO bit is one, the selected timeout value is in milliseconds.
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100 µ/ms
200 µ/ms
400 µ/ms
DISABLE
MXI Controller BTO Level
W8
a. 100 µs/ms MXIbus
System Controller Timeout
(Default Setting)
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100 µ/ms
200 µ/ms
400 µ/ms
DISABLE
MXI Controller BTO Level
W8
b. 200 µs/ms MXIbus
System Controller Timeout
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100 µ/ms
200 µ/ms
400 µ/ms
DISABLE
MXI Controller BTO Level
W8
c. 400 µs/ms MXIbus
System Controller Timeout
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100 µ/ms
200 µ/ms
400 µ/ms
DISABLE
MXI Controller BTO Level
W8
d. Disable MXIbus System
Controller Timeout
Figure 3-13. MXIbus System Controller Timeout Value Selection