HP 5501A Operating And Service Manual page 128

8.
Each card releases (allows to go high) OPC a s soon a s it is able.
NOTE
-
I n step 6 this card may drive DAV low at the same time or before it
IetsOPC go high. However the card in step 7 may not let OPC go high
until it has accepted the backplane information. OPC remains low
until all cards have released it.
-
9. When all cards have released OPC, INSV i s returned high to terminate instruction.
- -
10. DAV goes high if an output was involved. DAV remains high if no output was involved.
OPC is driven low by all cards.
11. Sequence starts over at step 1.
4.8 HP-IB BASED SYSTEM PROGRAMMING
HP-IB based transducer systems are supplied with the 9825A Calculator (for information on other
HP calculators, see Appendix A). The calculator systems include an HP-IB interface module and
appropriate ROM modules. The calculator documentation includes information for these devices.
Tables 4-2 through 4-77 show the instructions that can be issued to the laser system to control
system operation. These instructions are issued from the calculator via the HP-IB interface
module to the 10740A Coupler backplane bus. lnstructions consist of a numeric command and
an alphabetical address (e.g., 2 X causes the 10760A Counter card that has its address jumper
in the
X
position to output its last sample to the coupler backplane bus). The instructions must
be sequenced in the order that will cause the desired operations.
NOTE
In all programming instructions, 0 is zero and 0 is the letter 0.
lnstructions can be combined in one calculator program step. An example of this is the in-
struction sequence 102x30. From the tables it can be seen that the 1 0 instruction generates
a backplane sample command, the 2 X instruction causes the X-axis counter card to output its
sampled data and causes the HP-IB interface card to input that data, and the 3 0 instruction
causes the HP-IB interface card to convert that data to BCD and prepare to send the data to
the calculator upon receipt of further program statements.
Because the displacement data contained in the 10760A Counter cards (and, consequently,
the data sent to the calculator) is in units of
I/,
wavelengths of the laser light, the calculator
must convert this to a useable unit of measure
-
either inches or millimetres. Additionally, the
counters are preset to 160 counts so the effects of vibration do not cause the counters to under-
flow. The calculator, therefore, must also subtract 160 counts from the displacement data prior
to converting the data to inches or millimetres. One last data-manipulation requirement must
be satisfied by the calculator program: the displacement data must be multiplied by the velocity-
of-light compensation factor. The following formula demonstrates the procedure for conversion
of input counts from the 10760A Counter to compensated inches or millimetres. For accurate
measurements, the formula must be included in all calculator programs. Subsequent samples
show how this i s done.