Table 3-1, Control Register Channel Assignments - Racal Instruments 1260 VXI Manual

Control
Bit 7
Register
(MSB)
7
0
15
1
2 X
Module Operation 3-6

Table 3-1, Control Register Channel Assignments

Bit 6 Bit 5
6 5
14 13
X X
Setting a control bit to 1 closes the corresponding channel, and
clearing the bit to zero opens the corresponding channel. Thus, if
you write the value 1000 0101 binary = 133 decimal = 85
hexadecimal to Control Register 0, channels 0, 2, and 7 will close,
while channels 1, 3, 4, 5, and 6 will open.
The present control register value may be read back by reading an
8-bit value from the control register address. The value is
inverted. In other words, the eight-bit value read back is the one's
complement of the value written.
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 channel 13:
1. Read Control Register 1 (this register controls channels 8
through 15, with channel 8 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 13).
4. OR with 0010 0000 binary.
Channels
Bit 4 Bit 3
4 3
12 11
X X
X= not used, 1= close, 0= open
1260-152/172 User Manual
Bit 2 Bit 1
2 1
10 9
X X
Racal Instruments Ó2003
Bit 0
(LSB)
0
8
16