Issues in PIC16F1503

I am using PIC16F1503 for my automotive application. I want to understand few things:-

1)I have gone through through the schematic present in the "https://ww1.microchip.com/downloads/en/DeviceDoc/50002295A.pdf". In this, PIC 16F1503 is not having external oscillator. I want to know if it is possible to connect external crystal oscillator to PIC16F1503. If yes, which are the pin numbers to which external crystal oscillator can be connected? What is the difference if micro-controller runs on external crystal or on internal oscillator?

2)How to implement UART on PIC16f1503 ? I did not find any RX and TX pin on PIC16F1503.
3)How to implement OTA on PIC16F1503?

OSC1 & OSC2 pins see p44
No RS232 module

Look at the "Pin allocation table" on page 4; the last column gives the basic control signal connections:
eg. Pin 2 is clock input on the 14 pin version.

Also see the feature overview on page 7; the 1503 does not have a hardware UART included, so the only option with that specific device is to implement software serial.

That device also only has 128 bytes RAM, so not much for buffering any program transfer. The program memory appears to use 64 byte blocks, so you would need half the RAM for even one write buffer??

If you switch to the 16F181xx family they all have a hardware UART. The 16F18126 is a 14 pin device but with lots more flash and ram.

Mike.
Edit, this device not available until March.

Please tell me if PIC16F1503 is a good choice for automotive applications?

Probably not. you probably want a micro with can capability.

Mike.