I need to interface three 7 segment displays with 8085. Now I need to control each of them individually through a push button. The 7 segment display will run a counter and I will use the push button to turn on and then turn off the counter and then display the no at which i stopped. I need to do this with three different 7 segments and display all 3 numbers simultaneously.

Now I need to knwo whether I should create a separate output port for each display or whether it can be achieved by multiplexing them

 

Multiplex them.

 

What I/O ports did you have on your 8085 mpu? Do you have 8255 connected to the 8085 or you have connected latches like 74LS573 as output ports?

You can choose to multiplex the 3x 7 segment LED (10 IO lines) or directly connect them to the IO lines (21 IO lines) though 21 NPN or PNP transistors or 3x ULN2803 chips.

Allen

 

a 74HC244 buffer is good enough actually for small 7-segment displays.

Normally LED displays are multiplexed, and I'd recommend a 3-digit Module which already is multiplexed. They are not expensive.

Even for the sinks, I have sometimes used 2x LCX244 bit lines in parallel. It is OK since they are also updated in parallel.

No brightness variation, having such a sink.

Discrete transistors + resistors is quite a hassle.

 

Yes, 74HC244 can be used as input ports for 8085 too.

Allen