User manual

Appendix B Programmable Configurations
VXI-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
VXI-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 µs 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-MXI-2 is not
acting as the MXIbus System Controller. The BTO is also disabled
when the current MXIbus cycle maps to the VXIbus through a
VXI-MXI-2.
To change the MXIbus timeout limit of the VXI-MXI-2, write the
EEPROM byte at offset 2067 hex from the VXI-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 µs01
15 µs02
30 µs03
60 µs04
125 µs05
250 µs06
500 µs07
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