64 bit magnetic core memory system board

Schematic / Breadboard / Software

     The 1754 is a 64 bit magnetic core memory system board bringing together the family of core memory breadboard modules into a single pre-wired platform. The system board provides sockets for the X and Y drivers, a core memory sense amplifier, a PIC28 controller and of course the 64 bit memory matrix.

     The board is powered from a 12VDC power supply that feeds two regulator circuits: The first circuit provides a fixed 5V to operate the sense amplifier and PIC processor and the second circuit provides an adjustable DC voltage to operate the X and Y drivers (The "VM" rail). The drivers can be powered from 2.5 to 21V, essentially allowing the coincident current to be adjusted on the fly without changing the driver output resistors.

     The X any Y drivers use a fixed 10 ohms on each half bridge output to give a total bridge resistance of about 22 ohms or about 230mA for each X or Y line when driven at 5V. The coincident current of a selected bit is then about 460mA: For the cores available on this site, a coincident current of about 300mA is sufficient to flip a bit: 230mA (X or Y) is far enough below that threshold to prevent a single X or Y line from flipping bits unintentionally and 460mA (X and Y) is high enough to flip bits while also providing a robust "Flip" signal for the sense amplifier.

Modules:

• X and Y Drivers: 1749-10 x 4
• Sense amplifier: 1752
• Controller (PIC): 1746P
• Core matrix: 1747 with 1722, or 1747C

Input power:

• 12VDC via 5.5 x 2.5mm center positive barrel plug (not included)

On board power:

• 5VDC at 1A
• 1.23 to 10VDC adjustable at 1A (VM)
• Useful range of VM rail to operate the 1752 drivers is 2.5 to 21V.  VM is regulated on board to 3.3V to supply the logic circuits which are 5.5V tolerant.

Indicators:

• 1 monitor LED connected to processor I/O
• 4 sense amplifier output LEDs

Connector:

• 20 pin 0.1 x 0.1 shrouded header
• VM for drivers
• 5V for logic
• Ground
• Data bus D7:0
• 1 spare input to processor
• 2 spare I/O to processor
• Local plane EN/EN# signals (Not needed for a single plane)
• Sense amp common and 3 uncommitted sense amp inputs

Communication:

• USB to RS232 interface on the 1746 processor module