multiple 7-segment displays

[ico2]

hmmm, this seems like even if it can be done, it will be beyond my abilities to put it together, or it will take up a ton of protoboard space, or require special parts, i will see if it is acceptable to display the score in binary :S

 

[AllVol]

Perhaps you are right. Binary, decimal, hex or any other count system is going to be difficult, since you are asking for decision-making capability.

Short of microprocessor, I know of no single chip that can accomplish this.

 

[ico2]

Yeah, as I thought.

Huge thanks to ericgibbs, AllVol and mkh for their time.

 

[ericgibbs]

Hi,
Recapping so we get the terminology right.

The BCD counter value is parallel loaded into the 'score' shift register.

On each clock pulse the 'score' reg is shifted right, on the same clock pulse the 'high score' shift register shifts right.

A bit by bit compare of the two shift registers is made.

If the 'score' reg is > 'high score' reg then load 'score'reg into 'high score' reg [ the 'score' reg is empty ]

Display 'score' and 'hiscore' on 7 seg LED's

Suggestion:

If not already so, make the 'counter' a two decade [8 bit] also the 'score' shift reg 8 bit and the 'high score' reg 8 bit.

When its time, parallel transfer the 'counter' 8 bits into the 'score' shift reg.

Apply 8 clock shift right pulses to both shift regs, do your bit compare at the output of both regs.
Loop back on both SR's, so you don't lose the values.

If the bit by bit compare indicates that 'score' > 'high score' then select the data source to the 'hiscore' SR as the ouput of the 'score' SR clock both SR's [8 clks], so the 'score' data is clocked into the 'hiscore' SR.
else
no change
endif

The SR's types marked with *** are the functions you need to emulate in your logic.

I know that you don't want to use a PIC, but it would be ideal for this application.

This way of doing it is just PT.

Refer to attached dwg.

Eric

 

[ico2]

hmmm, I will see if there is an 8-bit counter hanging around, thanks

Yeah, the diagram is basically what I thought (bar the output).

 

[AllVol]

Hi,
If the bit by bit compare indicates that 'score' > 'high score' then select the data source to the 'hiscore' SR as the ouput of the 'score' SR clock both SR's [8 clks], so the 'score' data is clocked into the 'hiscore' SR.
else
no change
endif

This is where I kept running into a snag. How you gonna compare bit for bit to determine anything? As I see it, you would only get a true reply if all bits are the same (all on, all off, any exact combination). For a true comparison, one would have to perform a summing operation, i.e. if sumx>sumy then y=x else y=y. I know of no single chip that will do this short of a mpu; however, I suppose one might devise a circuit using a quad op amp in summing mode, but that's a bit beyond me.

 

[ico2]

Allvol:
I have already built that bit

 

[ericgibbs]

hi allvol,

Check out the 74LS85, 4 bit mag comp.

Used them in some projects, work fine.

Regards
Eric

 

[cadstarsucks]

Hi,
I spent a while googling and then searching these forums for how to do this and couldnt find anything.

I have a 7-bit binary number in a shift register and I want to display this number on a pair of 7-segment displays?

I do not yet know how to use microcontrollers, so using one in this project is not realistic.

Thanks

Short of using a programmable part, your best bet is a magnitude comparator feeding an adder and a subtracter feeding BCD decoder drivers.

If you use a magnitude comparator on the first nibble and use that to feed the carry input of an adder on the second nibble and to subtract 9 from the first nibble you will have your binary converted to BCD. Using just a comparator, two adders, and a quad AND to gate the -9 to the lower nibble adder or four chips plus your BCD-DEC decoder drivers.

Dan

 

[ico2]

right, I finally got this working today, by storing 2 4bit numbers in an 8 bit PIPO shift register.

Thanks guys

 

[Dave377]

The Xilinx link you're referring to is for an FPGA programmable device. Not discrete logic as IMO is needed for this question.

Very Nice reference though... Tnx, Dave

 

[cadstarsucks]

right, I finally got this working today, by storing 2 4bit numbers in an 8 bit PIPO shift register.

Thanks guys

There is another thing...you could make things a lot easier if you made it a BCD counter instead of a binary one.

Dan