7 segment LED w/MSP430 and CD74HC273 (serial display).
  8 digits screen (two lines by 4) based on two SN74HC595. Serial data exchange with MSP430, via 'Data' & 'Clock' lines.

Any questions - e-mail below.
Key - 7LED in subject.

  In contrast to the previous design, where there were only 5 "7-segment", the current one was made for a Geiger-Muller counter, where time is displayed on the top, and the current state of radiation level - below.

  The idea is the same. We push 16 bits into the line of flip-flops connected in series (by 'DATA' & 'CLOCK'). In addition, when 16 bits are pushed, 'WHITE' signal will pass them to output latches. It turns out a simple serial to parallel converter, whose outputs control the LEDs.

  74HC595's are 8 triggers connected in series, where the output of the last one comes to pin Q7'. Here you can connect the next 74HC595 ... and so on indefinitely. On schematic, two 74HC595 runs as 16-bit latch.
  Unlike 74HC273, internal trigger's outputs are connected to real outputs (Q0-Q7) via additional latches, which need to be controlled separately. It's simple. On the positive edge of WRITE signal data will be copied to output latches.

  The following picture shows the sequence on DATA & CLK lines, in order to reproduce 'c' symbol on the seventh indicator. Of course, shortly after you sent all 16 bits, you have to raise and lower the 'WRITE' signal, so that the digit appears on outputs Q0-Q7.

  As before, the screen update falls on the shoulders of MSP430. The micro controller does this job nonstop, 512 times per second (each digit is updated 64 tps).  To do this simply way, MSP430 runs from 32768 crystal and the WD timer awakens processor, precisely, each 1/512 sec.
 Coding is simple. The positive edge on a 'clock' line writes status of 'data' line to the first trigger.
The positive edge on a 'write' line overwrite output. One digit is shown at one time.

-------------Not finished yet.-------------

  What to show on the screen is a matter of fantasy and necessity. The important thing is that it's simple, and does not take much time for coding.

Dec.21,2017  SK_Lab


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