Microcontrollers - 16F vs 18F series

Hi, I am carrying out a project using RFID to read students tag, then sending it via Xbee from the reader to a computer. I am not quite sure which microcontrolelr series to use. I need the controllers in order to have communication between the RFID reader and the XBee, and from the XBee to the computer. Please give me some advice.

Thanks in advance.

Reading the RFID tags will require some simple decoding of the manchester code. Probably the best solution from perspective of the future project reuse is to attach some simple PIC controller to the RFID for decoding the data (12F100) and use some 16FXX for Zigbee communications. Of course you can put everything into a single controller, but having separate uP to RFID will make possible to create later many RFID projects without changing the reader at all.

if u want a single microcontroller to control what u have described and assuming ur RFID communicates using UART, u will need a microcontroller with at least 2 UART modules. for that, u will need at least PIC18F series.

Hi Friend

PIC16F series has interrupt with No Priority level
while
PIC18F series has interrupt with two Priority level(High Priority and Low Priority)

If in your project, you need interrupt with Priority
I suggest you PIC18F series.

Shyam
India

It also depends asm or c you gonna use

Hi,
PIC 18 has interrupt priority, PIC 16 does not.
PIC 18 is optimized for C, PIC 16 is not.
PIC 18 has more options for selecting a more rich set of peripherals than PIC 16.
The registers in PIC 18 have been changed to make them more easy than MOST PIC 16.

You could probably achieve your purpose with both.

Hope this helps.
Tahmid.

Hi,
There are a few more differences:

In PIC 18, you need not bother about bank switching, whereas in PIC 16, this is a real headache if you use assembly language and there is no way around it - it must be used.
PIC 18 has 8-bit data bus (same as PIC 16) but has 16-bit wide instructions, where as in PIC 16 it is 14-bit. So each instruction in PIC 18 is 2 bytes wide.
PIC 18 has hardware multiplier, PIC 16 does not.
PIC 18 has PLL option to multiply clock speed by 4, PIC 16 does not. In PIC 18, therefore, you can have a 10MHz crystal, use PLL to have a 40MHz clock and operate at 10MIPS, whereas in PIC 16, it will be 2.5MIPS for 10MHz crystal.
In PIC 16, maximum frequency for ECCP is limited to 20kHz. PIC 18 does not have this limitation.

Hope this helps.
Tahmid.

Check the New PIC16F1XXX devices they do not have the limitations you are talking about !.

PIC16F1XXX:

PLL * 4 : YES
8MIPS
NO BANK SWITCHING IF YOU WANT .. (for RAM)
AUTOMATIC CONTEXT SAVING ON INTERRUPT
STACK of 16 levels.
Much much more RAM.

Hi PaulHolland,

I don't understand your statement on "NO BANK SWITCHING IF YOU WANT .. (for RAM)"
i believe it need to use movlb x to switch bank if the variable is in another bank, unless the variable is accessbile by indirect addressing or all variables used are restricted to a single bank.

Regards,
Tom

With the new PIC16F1XXX fam of devices you can access all RAM in one large block using FSR0 or FSR1. Please see page in datasheet about: LINEAR DATA MEMORY PIC16F1824 for example. You can now also access ROM/FLASH program memory this way...

Hi,

In PIC18s, all Special Function Registers(SFR)+ few General purpose registers(GPR) are located in Access-bank;
You can access them in a single instruction (No need of bank selection or Indirect-addressing with FSRx). Also instruction set for PIC18 is more advanced. These features greatly simplify coding.

Also for communication several PIC18s have USB, 2 USARTs, CAN which PIC16 doesn't have.
All these for no significant cost change.