Constructing the new 1130 MRAM board today, part 1

FIRST STEP WAS THE POWER SUBSYSTEM

I installed the two linear voltage regulators which drop the 12V input power to deliver the two power rails for the board, 3.3V and 5V. A quick test with a bench power supply verified that they worked properly. I also installed the decoupling capacitors.

In addition to the power supply parts, I installed the power on reset logic since it sat beneath where the Digilent CMOD S7 FPGA board would be mounted. I soldered down sockets into which the FPGA board will plug. Below you can see the decoupling capacitors on the back side of the printed circuit board, plus a pair of resistors that drop the incoming +12V to an acceptable level to feed into the FPGA as a 'power available' signal. 

SOLDERING THE INTEGRATED CIRCUITS ONTO THE BOARD

I took advantage of the stencils I had from the prior invocation of the board to solder each chip using solder paste and a hot air gun. There were 13 chips to add to the board, but in today's session I only finished installing nine of them (excluding the power on reset and the linear voltage regulator chips). 

Five74LVC08 quad 2 input AND gates produce the 16 data and 2 parity output pulses. These will drive BVS52 transistors to pull down the 1130 sense output lines which in turn flip on a bit in the Storage Buffer (B) Register. Four 74HC86 quad XOR gates generate the correct parity for each 8 bit half of the 16 bit data word. These were installed today. 

In my next workshop session, I will solder down a 74HC00 quad NAND gate which implements a bit of glue logic for the design, two 74LV240 octal inverting tri state buffer gates, and the MR0A16A 1Mbit Magnetic Random Access Memory device. Once these are in place, the 18 BVS52 transistors with 18 pullup resistors will be soldered down. The final step is to transfer the 72 gold pins that form the three connectors into which the 1130 memory cables are plugged.