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Fig. 5. Current-temperature diagram. The inner boundary
curves represent measurements of 50 mils Si cores
with symmetric operation round the hysteresis loop,
(b) shows the temperature compensated drive
current. The outer curves (a) refer to asymmetric
operation at a constant polarization current
1P = 120 mA.
to three in a coincident current memory. The dVz
boundary curve of a current-temperature diagram
can thus be constructed after measurements at a
lower disturbing ratio (53 per cent) than must be
used in a coincident current memory (60 per cent),
fig. 5. In this diagram are shown the current margins
A Im and A I„ the last due to the back voltages when
all cores are switched. If a drive voltage Vd = 15
volts is used the actual memory can work reliable
at a maximum ambient temperature of 60°C.
A different type of current drive can considerably
increase the temperature region4. All the cores are
passed by a constant polarization current of
Ip — Ini.
The read current with an amplitude of 2/3 Im is
driven through the read wire in the same direction
as the polarization current. During the write phase
the write and help currents both have opposite
directions and an amplitude of 2/3 Im.
Core characteristics measured with this type of
drive at Ip = 120 mA are also shown in fig. 5. In a
similar way as earlier the current margins can be
calculated with respect to this type of drive. The
separation between the dVz and uV1 boundary curves
here allows a larger back voltage depending margin
A /,- so that a lower drive voltage can be used. The
total power dissipation of the memory circuits is
then reduced. A linear-selection memory can also,
using this type of current drive, work reliable at
temperatures much higher than 60°C.
References
1. Renwick W: A Magnctic-Core Matrix Store with Direct
Selection Using a Magnetic-Core Switch Matrix. Proc, IRE, vol. 104,
part B, 1957, pp 43C—444.
2. McMaiion R E: Survey of Memory Techniques Using Transistors.
Group Report No. 2G-24-82, March 1958, Lincoln Laboratory, MIT.
3. Törnquist J-R: On the Temperature Margins of a
Transistor-driven Coincident Current Ferrite Core Memory. Elteknik 2 (1959)
no. 6 pp 95—98.
4. Heijn II J, Troye N C: A Fast Method of Reading
Magnetic-core Memories. Philips Tech. Rew., vol. 20, no. 7, 1958/1959, pp 193
—207.
A Ferrite Core Memory for Storage of
Teleprinter Signals
Rolf von Campenhausen, Research Institute of National Defence, Stockholm
Ett koincidensminne för lagring av 1 024 ord med 5
bitar beskrives. Då låg kostnad har ansetts vara
viktigare än stor snabbhet, har drivkretsarna byggts
med lågfrekvenstransistorer. Accesstiden är därför
17 /us. Kretsarna har förenklats i största möjliga
utsträckning för att få en god tillverkningsekonomi.
Minnet kan även användas för lagring av signaler
för smalbands-TV om antalet matriser och
läskret-sar utökas.
The memory described in this article has been
built for storing teleprinter signals. It must be able
to send and receive such signals at a speed of
approximately 2 000 characters per second. For that
reason high speed was not of paramount importance
contrary to cost, simplicity and reliability. For this
621.318.042 : 621.394.324
purpose a memory of the coincident type with 5
matrices of 32 x 32 cores seemed to be the best
solution. As core drivers Telefunken transistors
OC604 spec, have been used because faster transistors
with the same current capacity are much more
expensive. For the same reasons Philips’ cores 6B1
were chosen. In view of the data variations of the
transistors the access time of the memory is 17 us.
If we make use of the hole-storage time of the
driver transistors the access time may be reduced
to 14 us. This time could be reduced to less than
5 us by the use of faster transistors and cores.
The cores were tested in a circuit that resembles
the most unfavourable conditions in the memory.
On one half of the cores a disturbed "one" and on
the other half a disturbed "zero" is pulsed, fig. 1.
.104 ELTEKNIK 1959
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