HP 4262A User Manual

Model 4262A
8-40. OPTION 004 COMPARATOR (A4, A5, &
A24). Option 004 adds A24 COMPARATOR CON-
TROL and the front panel control unit comprised
of A4 Thumbwheel Switch and A5 Comparator
Keyboard. The A24 Comparator Control manages
the control data set into the panel controls as well
as the decision data transferred from the nano-
processor so that comparison results are provided
(in three output configurations). The panel control
functions are managed in the following manner:
An instrument equipped with option 004 includes
a front panel control assembly which includes four
4 digit thumbwheel switches used to assign the de-
sired respective limits of L, C or R and D or Q. The
thumbwheel switch assembly provides output data
for each digit in a 4 bit code which correspondes to
the set number indicated in the control panel
window. To transmit the high and low limit data
from the thumbwheel switch assembly through an
8 bit digit data transmission line, the thumbwheel
switches are assigned 8 addresses (each set of four
digits occupies two addresses). The nanoprocessor
alternately accesses the thumbwheel switch output
code in the order of their address numbers. First,
Data Bus Driver/Receiver is set to receiver mode
and a 4 bit address code is stored in the Limit
Switch Select Code Register Ul1l. The Decoder
U10 sets its output logic (SS0) to low level in res-
ponse to the 4 bit address code (output logic of the
SS1 through SS7 outputs stay at high level). The
SS0 signal causes the 8 bit digit data to change
depending on the setting of the most significant
digit and third digit of the LCR HIGH LIMIT
switch that is first addressed. The digit data is
transferred to the nanoprocessor (passing through
the Data Bus Driver/Receiver set to driver mode).
Successively, the other digit data is transferred in
like manner. The commands of all pushbutton con-
trols on the A5 Comparator Keyboard are pro-
cessed during the interruption phase. The Interrupt
Flag circuit directs the nanoprocessor to act on the
interrupt request. When a comparator keyboard
control pushbutton is pressed, Gate UGA sets its
output logic to high level. This causes Flip Flop
U1A to generate an INT 3 output pulse. The INT 3
signal is sent to A21 Keyboard Control circuit
which forwards the interrupt requests to the nano-
processor. At this point, the comparator keyboard
signals access the nanoprocessor via the Data Bus
Driver
U17.
The nanoprocessor compares the measured values
with the limit numbers (values) and stores the deci-
sion data — the results of the comparison in An-
nunciator Register U3. The decision data is input-
ted, in parallel, to the TTL, Relay and Indicator
Lamp drivers.
841. OPTION 101 HP-1B COMPATIBLE (A25).
An instrument equipped with Option 101 HP-IB
Compatibility includes the A25 HP-IB INTER-
FACE board which provides the circuitry to.enable
intercommunications with external devices in
accord with IEEE-STD-488-1975 recommenda-
tions. The A25 circuitry is basically composed of
data bus driver/receivers and data registers which
provide the timely actions for handling the HP-IB
data bus input/output and control bus input/out-
put flow as directed by the nanoprocessor. Since
the circuit configuration is of general HP-IB
design and since general instructions on HP-IB in-
terface is otherwise readily available, a detailed cir-
cuit description is not given in this manual.

HP 4262A Specifications

General

Brand	HP
Model	4262A
Category	Measuring Instruments
Language	English