PIC16F887 vs PIC16F877A

PIC16F887 has the same pin diagram as PIC16F877A. Therefore, you can replace the PIC16F877A on your old project with PIC16F887 without any problem. What is so special about this new model of 8-bit PIC microcontroller? Let’s compare it side by side.

As the table shows, memory wise, both 887A and 887 are the same, whereby both have 8K words of program memory and 368 bytes of data memory. What attracted me to 887 is the internal crystal that offers speed from 32KHz to 8MHz. This internal crystal can be tuned through software register and it offers switchable operating frequency between internal and external crystal during program runtime. With this option, we can save the money needed for external crystal, avoid breakdown when the external crystal stop working and you have two extra I/O pin that was initially used for external crystal. The two extra pins are RA6 and RA7 which is bidirectional I/O pin, great! If you compare with PIC16F877A pin diagram you will not get these two pins.

What’s next? The ADC of course! PIC16F887 has increased the analog input to 14 channels, and every pin can be configured to analog or digital independently. As you might have notice, analog input is getting more important because more sensors come with analog output as it is the easiest method to deliver wide range of information by just single wire interface. These sensors include infrared distance sensor, Ultrasonic range finder, Accelerometer, Gyro, Gas sensor, LDR, and many more. With extra analog input, you are able to integrate more analog sensor into your design. Despite the increased number of analog input, there is another good feature in this model for those who do not need the analog input. In a scenario where some of you experience failure after you connect analog sensor to, let’s say, RA0 and RA5, digital input to RA2; and when you want to develop the program you notice that to make RA0 and RA5 become analog input, RA2 will become analog input too. Once the pin is analog, requesting digital logic will result in wrong info. 

However, you are still able to use it, provided that the program changes the analog pin to digital pin every time before it reads digital input pin, and same step apply when the program wants to read analog input pin. Isn’t it troublesome? Many would agree with me. Worry no more with PIC16F887 as the selection of analog input or digital input pin are truly independent of each other. PIC16F887 uses ANSEL and ANSELH register to configure 14 channels of AN pin to analog input or digital pin. ANSEL controls eight pins of PORTA+PORTE while ANSELH controls six more pins at PORTB.

OK, what else can we get? If you have noticed, there is one I/O pin left out from previous discussion. This pin is RE3. PIC16F877A offers 33 I/O pin while PIF16F887 provides 36 I/O. We know two extra I/O are from the crystal pins, where is another? It is actually the MCLR pin which we normally use it for Reset purpose. For PIC16F887, user may have the choice to tie MCLR internally to VDD and use pin 1 as RE3. However, this pin can only be used as digital input.

I think that those facts mentioned are sufficient for me to replace my PIC with this new model, but there is another important factor for me to consider before migrating to it. Everyone would agree with me, of course that is the price. PIC16F887 is much cheaper than PIC16F877A. You should be able to get a PIC16F887 with only half the price of PIC16F877A. This is the main factor, more features yet cheaper price; with this, we definitely have no reason to resist it.