Appendix B
Programmable Configurations
VME-MXI-2 User Manual
B-8
© National Instruments Corporation
MXIbus Timer Limit
The MXIbus Bus Timeout (BTO) is a watchdog timer for transfers
on the MXIbus. The MXIbus BTO unit operates only when the
VME-MXI-2 is acting as the MXIbus System Controller. The
functionality is similar to that of the VMEbus timer limit 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 VME-MXI-2 is not
acting as the MXIbus System Controller. The BTO is also disabled
when the current MXIbus cycle maps to the VMEbus through a
VME-MXI-2.
To change the MXIbus timeout limit of the VME-MXI-2, write the
EEPROM byte at offset 2067 hex from the VME-MXI-2 base address.
The following table gives the value that should be written for the
corresponding time limit.
Time Limit
Value (hex)
Timer Disabled
00
8
µ
s
01
15
µ
s
02
30
µ
s
03
60
µ
s
04
125
µ
s
05
250
µ
s
06
500
µ
s
07
1 ms
08 (default)
2 ms
09
4 ms
0A
8 ms
0B
16 ms
0C
32 ms
0D
64 ms
0E
128 ms
0F
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