The PIC16F1789-I/PT is a 8-bit 28-pin Advanced Analogue Flash Microcontroller with high-performance RISC CPU. During interrupts, certain registers are automatically saved in shadow registers and restored when returning from the interrupt. This device has an external stack memory 15-bits wide and 16 words deep. A stack overflow or underflow will set the appropriate bit (STKOVF or STKUNF) in the PCON register and if enabled will cause a software reset. There are two 16-bit file select registers (FSR). FSRs can access all file registers and program memory, which allows one data pointer for all memory. There are 49 instructions for the enhanced mid-range CPU to support the features of the CPU. The enhanced mid-range core has a 15-bit program counter capable of addressing a 32k x 14 program memory space.