Tektronix 7834

R-8
R-9
R-10---
PROGRAM FOR 100 MV, INVERTED, CALIBRATED
(UNCALIB-
RATED OPERATION
SHOWN BY SHADED AREA)
1195-34
Figure 3-35 . Idealized current waveforms of
(A)
Row
analog data
and (B) Column analog data .
The final data output is provided from time-slot 9
by R190
connected to the column output and R90
to the row out-
put . These resistors encode two units of column
current and
four units of row current to cause a V (volts) to be
display-
ed . Time-slot 10 is not encoded, in accordance with
the
Standard Readout Format . The resultant crt readout will
be
+ 100 /V .
In the above example, the row analog
data was programmed
to define which row of the Character Selection
Matrix was
addressed to obtain information in each
time-slot . The
column data changes to encode the applicable readout
data
as the
operating conditions change . For example, if the
variable control
of the plug-in unit was activated, R130
would
be connected between time-slot 3 and the column
analog
data output line . This encodes 10 units of column
current (see shaded
area in time-slot 3 of the waveform
shown in Fig . 3-35) . Since
one
unit
of row current is also
encoded during this time-slot by
R30, a > (greater than)
symbol is added to the display
.
The
crt readout will now
show + > 100 MV . In a
similar manner, the other switches
can change the
encoded data for the column output and
thereby change the
readout display . See the descriptions
which follow for
decoding this information .
Column and Row Data Switches
Theory of Operation-7834
The column analog data encoded by most plug-in units can
be modified by attenuator probes connected to the input
connectors of amplifier plug-in units . A special coding ring
around the input connector of the plug-in unit senses the
attenuation ratio of the probe (with readout-encoded probes
only) . The probe contains a circuit that provides additional
column current . For example, if a 10X attenuator probe is
connected to a plug-in unit encoded for 100 microvolts as
shown in Figure 3-34, an additional unit of current is added
to the column analog data during time-slot 1 . Since two
units of current were encoded by R111, this additional cur-
rent results in a total of three units of column analog cur-
rent during this time-slot . Referring to the Character
Selection Matrix (Fig . 3-27), three units of column current,
along
with the two units of row current encoded by R 10,
indicates
that the prefix should be shifted one column to
the left . Since this instruction occurs in the
same time-slot
that previously indicated that two zeros should be added to
the display and only one instruction can be encoded during
a time-slot, the zeros do not appear in the display
.
The crt
readout will now be changed to 1 mV
(readout program
produced by plug-in same as for previous example) .
Three other lines of information are connected from the
plug-in compartments to the Readout System . The column
and row analog data from channel 2 of a dual-channel plug-
in are
connected to the Readout System through terminals
A38 and
B38 of the plug-in interface, respectively . Force
readout
information is encoded on terminal A35 ; the func-
tion
of this input is described under Column and Row Data
Switches . The preceding information gave a typical example
of encoding data from an amplifier plug-in unit . Specific
encoding data and circuitry is shown in the individual plug-
in unit
manuals .
The encoding data from the plug-in units is connected to
the Column
and Row Data Switch stages . A column-data
line and
a row-data line convey analog data from each of
the 8 data sources (2
channels from each of the 4 plug-in
compartments) .
The Column Data Switch U3262 and the Row Data Switch
U3232 receive the Channel Address Code from the Channel
Counter, refer to diagram 10 at the rear of this manual . This
binary
code directs the Column Data Switch and the Row
Data Switch
IC's as to which channel should be the source
of the encoding data
. Table 3-5 gives the eight combinations
of the Channel Address
Code and the resultant channel
selected with each
combination
.
These stages have nine
inputs and provide
a time-multiplexed output at pin 7,
which includes the information from
all of
the
input chan-
nels . Eight of the nine inputs
to each stage originate in the
plug-in units ; the ninth input comes from
a special clata-
encoding network composed of
Resistors R3241 through
R3248 and R3251 through
R3258 . (See Zeros Logic and
Memory description for
further information on ninth
channel .)
3- 45