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AM2540 Module - Eµ Memory Address Generator (MAG)
Overview This module is a clone of the Memory Address Generator in the Eµ Systems Modular Sequencer. It is a very close replica with only minor changes to use modern
components and to add some new features.
The MAG is a 512 step position counter. A positive going pulse on the UP input jack moves the position forward by one step. Similarly a pulse on the DOWN input jack moves the position back
one step. A pulse on CLOCK INHIBIT stops the count, and a pulse on RESET puts the counter back to position 0. There are front panel pushbuttons that replicate the jack functions and the UP and DOWN pushbuttons will fast forward/backward
the counter position when held down. The display shows the current position in Octal, 000 – 777.
As the 2500 series is a modular sequencer, there is no onboard clock for sequencing the channels,
so a VCC/8PAG should be used. The MAG generates a 9-bit binary code for addressing memory units like the 2545. This is available on an internal 16-pin DIL socket
Original Circuit The original design dates back to late 1973,
and I have cloned the Version 2 schematic of February 1975. The core of the circuit is a couple of 74C193 counters and an additional 4013 flip flop that creates the 9-bit address code. A set of CMOS 4013's provide the front panel controls.
A rather nice but small 7 segment bubble LED display is driven by a 7447 and the 3 digits are multiplexed by a CMOS clock and two 74C157's. The LED display is a common cathode HP5082-7433, which displays three red digits 2.5mm high.
AM Circuit The AM circuit is exactly the same except for some upgrades and enhancements:
- HC CMOS chips
- 4069 CMOS instead of 74C04
- 4532 LED driver chip instead of 7447 and transistors
- Emulator 2 type push button switches
The circuit has been split over three PCB's; LED, COUNTERS and LOGIC. The front panel is similar
to the original. There is no trimming.The circuit needs +5V for the CMOS logic, derived from the normal MOTM power connection.
Front Panel
The front panel is a standard AM design, 90mm wide and 4U high, with black lettering. Controls knobs are standard Eµ Modular designs.
Build History
The schematic was transferred into Eagle CAD in the summer of 2005 when I was on holiday in the Peak District (UK). The circuit has been laid out over 2 80x100mm PCB's and a prototype of the LED PCB is currently being tested. The 3 digit LED display and 4532 driver have already been tested ok.
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