Racal Instruments 1260-22 User Manual page 33

1260-22 User Manual
Module Operation 3-6
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Relays are closed when the corresponding control bit is set to 1
and are opened when the corresponding control bit is cleared to 0.
Thus, if you write the value 1000 0101 binary = 133 decimal = 85
hexadecimal to Control Register 0, relays K1, K3, and K8 will be
closed, while relays K2, K4, K5, K6, and K7 will be opened.
The present control register value may be read back by reading an
8-bit value from the control register address.
inverted by the 1260-22 hardware. This means that if you want
to change the state of a single relay without affecting the present
state of the other relays controlled by the control register, you
must:
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 relay K14 (Channel 13)
1. Read Control Register 1
2. Invert the bits in the value read in step 1
3. AND with 1101 1111 binary
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 1260-22 module.
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The value is