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Alternate to MM74C926

HighTechPower

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Hi I'm searching for an easily available IC like MM74C926 with exception that instead of incrementing the counter using CLK, it takes BCD input and display the numbers. The issue is it should be 4 digit display like the mentioned IC but latch BCD data on correct seven segments, out of those four, using some input logic.
 

betwixt

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You can't use anything like a 74C926 for that purpose, it doesn't have provision to select which digit you want to display.
If you are wanting something to multiplex four display digits you need the device to be able to store the digits in memory and repeatedly read them out to the display segments. A small MCU would do the job easily.

Brian.
 

danadakk

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Questions :

1) Do you want BCD digit data input muxed ?
2) Do you code, use micros ?

Regards, Dana.
 

HighTechPower

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Questions :

1) Do you want BCD digit data input muxed ?
2) Do you code, use micros ?

Regards, Dana.

Thank you Dana.
Yes I want BCD data to be muxed.
and yes I knows coding and PIC micros.
Recently I got a project in which I have to display 4 digits using BCD (or decimal). Today I just gone through MMC74C926 and was impressed how it is multiplexed and requires only this IC for four digits display.
 

KlausST

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Hi,

Maybe you can have somebody to program a PLD for you.
Shouldn't be difficult nor expensive.

Klaus
 

danadakk

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One method using a PSOC -

1614644557875.png

This is single chip except external Rs in the segment lines to set current. For mA kinds of small LED
displays, larger ones would require external buffers. This requires you add a interrupt to a port
to handle incoming BCD value and digit number, to hold in memory, and feed to the looping
display routine. Very simple code. Or use DMA to essentially eliminate code, DMA incoming values
to memory, and back out again to display routine. Or build an actual Verilog implementation
of desired behavior., can also be done with schematic capture. All single chip. Could bring data
in serially, USB, I2C, UART, SPI.....as well. And add special display patterns for the non 0 -9 values,
using onchip LUT....many possible variations of how to do this.

1614645043848.png


Regards, Dana,
 

BradtheRad

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You can multiplex 4 digits through a 4511 (or 4543) IC by feeding it 4 nibbles in sequence, while activating each digit independently in sequence. You need a flag signaling the start of a sequence so you can reliably begin displaying at the first digit.

This article appears relevant. The BCD values come from whatever source you prefer. The 7-segment digits are activated one at a time by a ring oscillator (chaser, sequencer). An Arduino is not essential.

 
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danadakk

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For consideration in future stuff.

This is a PSOC which has an ARM core + Logic Fabric + Analog Fabric on a chip.

So you drag and drop functions onto a canvas, wire them up, and using APIs control
the functions. In this instance no code is needed,

It has a facility to make custom functions, which I did in this instance, the BCDdigit block.
You can make your own function with schematic capture, or Verilog, or both. In this case
I did it in schematic capture just drag and drop logic elements, like D's and muxes and gates.

What you see is basically an ability to write to latches digit values, then that is fed to a LUT
to create the 7 segment data from BCD values.

I did not add the scan function, eg. a 2 bit counter to round robin the muxing of the digits
out to the display, just ran out of time. But thats trivial as well. Lots of fun. Board to use is
~ $ 10 - $ 15, compiler and tool is free.

1614696780918.png


This design is codeless. Note you still hit the build button so that the routing gets done,
and chip default setup stuff occurs, which normally you do not have to touch. You can
see in right hand window resources used/left, and most are unused in this case.

You can easily add the chips COM stuff so digit data comes in over a serial link.........
whatever.

This is single chip.


Regards, Dana.
 

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