German Logic diagrams

Original German Logic diagrams for the Söemtron 220
These drawings are courtesy of Bernard Green, they include component references and values, logic symbols and a logic diagram for each of the twelve logic boards in a Söemtron 220. They however do not include the keyboard or display boards. These drawings give an insight into the what the logic designers at V.E.B. Büromaschinenwerk Sömmerda were able to achieve in the functions of the Söemtron ETR 220 with such basic, albeit almost primitive electronics then available in 1960's German Democratic Republic. There are several small documentation errors in these diagrams which we will list once the circuit to logic checking process is complete. We freely acknowledge the intellectual property rights of the design of the Söemtron ETR 220 and that this resides with V.E.B. Büromaschinenwerk Sömmerda (1) and their designers.
 
Circuit symbols -
GatesAND - OR Gates
Buffers - 1Buffers
Buffers - 2More buffers
Delays and FlipFlop inputsDelays and FlipFlop inputs
Basic FlipFlopsBasic FlipFlops
MonostablesMonostables
Schmitt TriggerSchmitt Trigger
Clock oscillatorClock oscillator
Core driverCore driver
Core sense amplifierCore sense amplifier
Nixie tube driversNixie tube drivers
Power supplyPower supply
 
And the boards -
Board 12Display Cathode Drivers, numeric key encoding
Board 11Display Anode Drivers, function key encoding
Board 105 bit display "Z" counter
Board 9F2,5-6 function latches, including register addressing
Board 8F1/3, VER and MZ function latches
Board 7B1-4, VOR and R function latches
Board 6Control gating
Board 5V, SCHRIEB, S1 function latches and 25Khz clock
Board 4Arithmetic unit E Register (input), Carry latch and digit drives 0/1
Board 3Arithmetic unit A Register (output), digit drives 5-9
Board 2Core memory drivers, Read, Write and Inhibit decoding
Board 1Core store, read amplifiers and digit drives 2-4
  1. V.E.B. = Volks Eigener Betrieb, or Peoples Owned Company.      back
  2. Büromaschinenwerk = Office Machine Works.      back

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