how to increase I/O pins in microcontroller

[devmania]

Hi everyone,

Can anyone tell me how to increase the i/o pin in a microcontroller at89c51?
what should i interface and how to do it?

Thank you.

 

[saidutt]

Hi everyone,

Can anyone tell me how to increase the i/o pin in a microcontroller at89c51?
what should i interface and how to do it?

Thank you.

hi,

you cannot increase the IO pins for 8051 .

but your can use the 8051 micro-controller IO pins efficiently by using a decoder (or) by using few protocols like I2C,CAN, .. and so on.

it is only option

 

[mishra12]

you mean like this

 

[harishwww]

if i/o pins are increased the process will be slow so how to overcome or solve this factor

 

[FvM]

I think there are two limitations:
- speed of a particular I/O extension, e.g. serial or parallel interface. Use the technique that's adequate for the respective purpose
- total processing capacity. if it's exceeded by the application requirements, change the processor

 

[qwertyuiop415263]

If you need more I/O pin then use a controller having more I/Os. e.g Pic controllers
come with different number of I/O. 18pin 18f1220 have two I/O ports , 40pin 18f452 has five and 80pin 18f8525 has 11.

 

[kkkollapudi]

Usage of shift registers to add additonal I/Os on board requires more processing time,

You can reduce the processing time by using 8-bit Octal transperent latch (ex. 74ls373) for output port, use 74LS244 for input port, with a decoder (2x4).

Here you need to spare one 8-bit port and two more I/O lines ( to control decoder)

Please let me know if you have still queries.

 

[Kurenai_ryu]

don't forget the old 8255

 

[mishra12]

here is a pic of expansion of i/o port 89c51 controller in this pic you can see clearly white female connector in the center of pcb is input from keyboard (8*12)not seen and on the left side three uln2003 for relay out puts ,chip using 12mhz crstal,and other chips ( x-ray equipment control panel )and lcd connection 16*2

 

[jit_singh_tara]

use port expander mcp23s17 or mcp23017

 

[spiralbrain]

don't forget the old 8255

yes it still rules, if you can get your hands on one. :smile: