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1260-X138 User Manual
Module Operation 3-8
Racal Instruments
©
2005
1. Read the control register
2. Invert the bits (perform a one’s complement on the register
data)
3. Perform a bit-wise AND operation, leaving all but the
specific control register bit for the relay to change
4.
To open
: continue to step 5.
To close
: OR in the bit for the
relay to close.
5. Write the modified value back to the control register.
For example, to close channel relay K90:
1. Read Control Register Group 3 (this register controls K85 –
K92 with K85 represented by the LSB)
2. Invert the bits in the value read in step 1
3. AND with 1101 1111 binary (the zero is in the position
corresponding to channel 63)
4. OR with 0010 0000 binary
5. Write the value to Control Register 1
The VISA I/O library may be used to control the module. The VISA
function
viOut8()
is used to write a single 8-bit byte to a control
register, while
viIn8()
is used to read a single 8-bit byte from the
control register. The following code example shows the use of
viOut8()
to update the 1260-X138 module.
Configuring
Larger
Multiplexers
The 1260-X138 is normally configured as eight 1x8 multiplexers.
However, the plug-in contains seven special configuration relays
that interconnect two or more multiplexers to form larger
multiplexers.
Figure 2-1
shows these relays, identified as K64
through K70.
Table 3-1
provides the control register access
information for these relays. Each configuration relay connects the
commons of two multiplexers together.
Configuration may be done “on-the-fly” if desired.
As a configuration example, suppose you require two 1x16
multiplexes and one 1x24 multiplexer. You may form these
multiplexers from a 1260-X138 by configuring it as follows:
1. Combine muxes 0 and 1 to form a 1x16 multiplexer. To do