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Section
2-7M13
THEORY
OF
OPERATION
INTRODUCTION
The 7M13 Readout Unit provides front panel operation
of
the readout system of any Tektronix 7000
series oscilloscope. It
will
operate
in
any plug-in position
in
the
oscilloscope mainframe. The readout
display
will
appear on
the
CRT
in
the
position associated with the selected plug-in compartment. Refer
to
the mainframe service manual for the readout system circuit description and
to
diagram 1
in
this manual for
the following circuit description.
THEORY OF OPERATION
The WRITE pushbuttons select either the UPPER or
LOWER
(channels 1 and 2 respectively) memory
IC's for data storage. This routes the
output
of
U202B through U168C for the UPPER and through U168D
for the
LOWER
channel selection. The signal
is
then presented
to
the appropriate column and row memory,
write enable inputs.
Each channel has a ten character capacity.
As
each successive character pushbutton
is
pressed, the
output
of
U132C causes U198
to
advance its count
to
the next character position address. This continues
until
all
character positions are filled. U129B locks
in
the tenth position and
is
reset by pressing ERASE.
Pressing a character button when
all
ten positions are filled
will
cause the tenth character
to
be replaced
with the newly selected one.
The ERASE pushbutton, when pressed, fires single-shot U170B. The pulse from U170B clears U129B
and allows pulses derived from time slot information (output of U163D)
to
be presented through U168A,
U168B, and U132C
to
U198 (address-to-memory). The
output
of U168B
is
also presented
to
the
write-into-memory circuits. These pulses cause U198
to
count through all data addresses, while the
write-into-memory circuits allow the data present on
the
data inputs
to
the row and column IC's
to
be
written into the memories.
No
data
is
present on the inputs
to
the memories during ERASE. This
"no
data"
condition
is
interpreted
as
a skip commantl and results
in
a blank display for
that
channel.
When
single-shot
U170B returns
to
its normal state,
it
triggers single-shot U170A
to
reset U129B and the address-to-memory
counter, U198.
Time slot pulses 2 through 10 are routed through
0177
and
0185.
These pulses are used
to
advance
U195, the read from memory address
IC.
Time slot 1
is
routed through
0190
and
is
used
to
reset U195
at
the end
of
each count.
The address multiplexer (U200) determines which address, either time slot (output
of
U195)
or
data
(output
of
U198), will be directed
to
the memory select inputs. Normally, U200 directs time slot addresses
to
these inputs for data readout, however, when a character pushbutton
is
pressed on the front panel
of
the
Readout Unit,
the
output
of
U202A causes
the
multiplexer
to
switch and read the address
at
the outputs of
U198.
Pressing a character button supplies ground closures
to
the inputs
of
U109 (column data) and U103 (row
data). U109 and U103 are decimal-to-BCD converters. They generate the coded character information
presented
to
the memory data inputs; column data
to
U280 and U260, row data
to
U240 and U220.
Since
all
characters generate column data, the outputs of U109 (through diodes CR109, CR110, CR111,
and CR112) are used
to
inititate the write-into-memory command signals and
to
trigger the
address-to-memory. This signal, through U202A,
is
also used
to
switch the address multiplexer (U200) from
the read-from-memory address (output
of
U105) so
that
data stored
in
the memories can be read and
2-1
Scans by ArtekMedia © 2008
L
L
r .
I
L
i
L-
®
Section
2-7M13
THEORY
OF
OPERATION
INTRODUCTION
The 7M13 Readout Unit provides front panel operation
of
the readout system of any Tektronix 7000
series oscilloscope. It
will
operate
in
any plug-in position
in
the
oscilloscope mainframe. The readout
display
will
appear on
the
CRT
in
the
position associated with the selected plug-in compartment. Refer
to
the mainframe service manual for the readout system circuit description and
to
diagram 1
in
this manual for
the following circuit description.
THEORY OF OPERATION
The WRITE pushbuttons select either the UPPER or
LOWER
(channels 1 and 2 respectively) memory
IC's for data storage. This routes the
output
of
U202B through U168C for the UPPER and through U168D
for the
LOWER
channel selection. The signal
is
then presented
to
the appropriate column and row memory,
write enable inputs.
Each channel has a ten character capacity.
As
each successive character pushbutton
is
pressed, the
output
of
U132C causes U198
to
advance its count
to
the next character position address. This continues
until
all
character positions are filled. U129B locks
in
the tenth position and
is
reset by pressing ERASE.
Pressing a character button when
all
ten positions are filled
will
cause the tenth character
to
be replaced
with the newly selected one.
The ERASE pushbutton, when pressed, fires single-shot U170B. The pulse from U170B clears U129B
and allows pulses derived from time slot information (output of U163D)
to
be presented through U168A,
U168B, and U132C
to
U198 (address-to-memory). The
output
of U168B
is
also presented
to
the
write-into-memory circuits. These pulses cause U198
to
count through all data addresses, while the
write-into-memory circuits allow the data present on
the
data inputs
to
the row and column IC's
to
be
written into the memories.
No
data
is
present on the inputs
to
the memories during ERASE. This
"no
data"
condition
is
interpreted
as
a skip commantl and results
in
a blank display for
that
channel.
When
single-shot
U170B returns
to
its normal state,
it
triggers single-shot U170A
to
reset U129B and the address-to-memory
counter, U198.
Time slot pulses 2 through 10 are routed through
0177
and
0185.
These pulses are used
to
advance
U195, the read from memory address
IC.
Time slot 1
is
routed through
0190
and
is
used
to
reset U195
at
the end
of
each count.
The address multiplexer (U200) determines which address, either time slot (output
of
U195)
or
data
(output
of
U198), will be directed
to
the memory select inputs. Normally, U200 directs time slot addresses
to
these inputs for data readout, however, when a character pushbutton
is
pressed on the front panel
of
the
Readout Unit,
the
output
of
U202A causes
the
multiplexer
to
switch and read the address
at
the outputs of
U198.
Pressing a character button supplies ground closures
to
the inputs
of
U109 (column data) and U103 (row
data). U109 and U103 are decimal-to-BCD converters. They generate the coded character information
presented
to
the memory data inputs; column data
to
U280 and U260, row data
to
U240 and U220.
Since
all
characters generate column data, the outputs of U109 (through diodes CR109, CR110, CR111,
and CR112) are used
to
inititate the write-into-memory command signals and
to
trigger the
address-to-memory. This signal, through U202A,
is
also used
to
switch the address multiplexer (U200) from
the read-from-memory address (output
of
U105) so
that
data stored
in
the memories can be read and
2-1
