Computer-Controlled Thin-Film Matrix Image-Digitizing System. Page: 3 of 9
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and horizontal synchronization for the display
The scan control logic synchronizes the
address register. the horizontal (matrix line)
sift register, and the vertical (matrix bit)
shift register. Under proper conditions, it
generates a muster reset signal whic effectively
sets all registers to point (0,0) on the matrix.
The first clock pulse then generates a parallel
entry signal which sets all registers to (1.1).
the next pulse steps to (1.2). etc.. and
rentinues to scan the matrix one point at a time.
The horizontal and vertical shift registers
i are identical, the vertical one operating at the
lower rate, with 1 shift per 176 shifts of the
horizontal, In each register there are actually
two shift registers, a 16-bit one and an 8-bit
one, with outputs logically intersected in the
reading unit to form the equivalent of a
128-bit shift register.
- The reading unit alone contains buffers,
MD-gates. Switches, the photo-satrix itself.
and a discriminator-amplifier. Input logic
sigrAls from the scanning unit ire buffered from
TIL levels to various levels required by each -
set of switches. Representative matrix rcad
unit circuitry is shown in Fig. 4. The anode
switches are bipolar transistors with AID-gate
action on suitter and base inputs. The collector
is connected directly to an anode line of the
matrix. A diode-resistor AND-gate is used with
an FET to switch the cathode lines of the matrix.
This FET is an HE566. p-channel enhancement-
mode device with a source-drain capacitance of
about 0.08pF and a gate-drain capacitance of.
about 0.3pF. The drains of all of the FET
switches are coiron and connect to the emitter
of a caoaon oese amplifier. The collector
S output of this amplifier is amplified by the
tbdel 702 operational aplifier with a variable
threshold control ors its other input. The
output of this amplifier is matrix data which
is tren gated by the input-output logic in the
scanning unit for reading by the computer or
-for video display or for both. -
is given. A complete list of steps as each
occurs during one complete matrix scan and read
operation from start to finish is listed next:
PDP-8 to Response from
1 H scan, read, and store
E end program, complete
2 Four digit identification
4 0 " display matrix read
4 0 " transmit
6 R " write digitized information
on magnetic tape
thus. existing software features provide the
capability of restarting the matrix scan and read
process at any potit in the operation. Each
digitization scan has its own unique four digit
numerical identification. The operator may elect
to display the data as stored by the POP-8
immediately op a Tektronix Display Oscilloscope
-.ltdel RH602. This provides visual indication of
the overall digitization as compared to the video
display mentioned above. Provision is also made
for transmitting over the LLL Octopus system from
a remote terminal. but this part of the system
has not been used. After the operator decides to=
continue and desires to record the information
from one matrix read for further processing on a ,
larger computer. the data is written'with a
Kenmedy Model 1600 magnetic tape unit onto an
eight inch diameter seven track magnetic tape.
This tape provides a permanent store at the PDP-8.
since succeeding "reads' continue to use the same
core space in memory, and consequently this main
storage area is cleared after each run to prevent
duplication. Data from a single run is packed
conveniently into about 2000 words with associated
line and bit counts being stored. The program
itself occupies a like amount of core. with
approximately 3000a words taken.
Processing Computer Program .
After the respectide images have been d.gi-
The Control Program tized and, through the preceding PDP-8 set of
program,. have been transferred to a media of
This software package constitutes a permanent storage, such as magnetic tape or disk,
controllIng main program with interaction-aong the data itself is readied for further processing.
the mijor elesents of the system. The on-line
teletypewriter provides operator command to the At ILtL this further processing is accasp-
PDP-8. This interaction ;ives an operator a. lashed by a large general purpose computer, such
certain eamunt of flexibility in determining M the COC 6600. Here, for example. each one-half
rhic part of the digitizing operation to start inch seven track tape used would contain several
(0,c repeat) digitized images in the pre-established BCD packed
format. Processing of this raw output data may be
The controlling program sends a message to constred as.a two-pass operation. The first
the teletypewriter and awaits an appropriate pass converts the raw binary BCD data into a disk
response from the-operator. It rill continue file with the specific format of twelve octal
and produce a read of the matrix unless a wrong control words followed Imediately by the estab-
eamand is given which then immediately causes wished file data points. The second pass results
a return to start. In fact, if the response is in further processing of the created file so as
not correct at any given point in the coamuni- to establish a new format suitable for printing.
cation, a diagnostic is sent to the operator presenting the data.for view on a graphics monitor
advising him of an error and a return to start display, or to CRT output for hard copy paper pbts
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Martin, L.; Gadd, T. & Baker, T. Computer-Controlled Thin-Film Matrix Image-Digitizing System., report, January 1, 1971; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc1036107/m1/3/: accessed October 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.