[SOLVED] Extend OUTPUT pins of a PIC microcontroller with the help of output shift register

Extend OUTPUT pins of a PIC micror with the help of output shift register 74HC595

Expert opinions will be very much appreciated with due respect to update this project.
This is how I have extended the pins of a PIC16F84A microcontroller with the help of an output shift register (IC 74HC595) which I have used in another project to display ASCII characters using 8x8 (or 5x7) MATRIX. Project is working fine. Do I need any modification?

;Following is the code to switch on alternate LEDs for 1 seconds


;;;;;;;;;;;;;;;;;1 sec delay;;;;;;;;;;;;;;;;;;;;;;;
DELAY1s
Delay_01

MAIN
LUPHR
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;HC595.inc;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;Thanks to Nebojsa Matic of mikroElektronika for idea
;Var variable whose contents is transferred to outputs of shift register.
;Var1 loop counter
;Here 8bit data is used, so VAR1 gets decimal 8 to continue the loop for 8 times

HC595 MACRO VAR,VAR1
LOOP

The schematic is given below:-

If I understand correctly you have 8 leds connected at the outputs of 74HC595.

According to the datasheet the max current for each pin is 35mA so you have no problem with that but note that the total Vcc current max is 70mA so if all your leds turn on at the same time then you may have a problem.

Alex

Mr. Alex,
Thank you very much for your comment.
By chance I never have turned on all the LEDs at the same time. That’s how I managed to escape possible problem. Surely I will follow your suggestion.