We can Read Microchip Microcontroller PIC18F4450 Program, please view the Microcontroller PIC18F4450 features for your reference:
If both low and high priority interrupts are enabled, the Stack registers cannot be used reliably to return from low priority interrupts. If a high priority interrupt occurs while servicing a low priority interrupt, the Stack register values stored by the low priority interrupt will be overwritten. In these cases, users must save the key registers in software during a low priority interrupt.
If interrupt priority is not used, all interrupts may use the Fast Register Stack for returns from interrupt. If no
interrupts are used, the Fast Register Stack can be used to restore the STATUS, WREG and BSR registers at the end of a subroutine call. To use the Fast Register Stack for a subroutine call, a CALL label, FAST instruction must be executed to save the STATUS, WREG and BSR registers to the Fast Register Stack when Read Microchip Microcontroller PIC18F4450 Program.
A RETURN, FAST instruction is then executed to restore these registers from the Fast Register Stack. There may be programming situations that require the creation of data structures, or look-up tables, in program memory. For PIC18 devices, look-up tables can be implemented in two ways:
- Computed GOTO
- Table Reads
A look-up table can be formed with an ADDWF PCL instruction and a group of RETLW nn instructions. The W register is loaded with an offset into the table before executing a call to that table. The first instruction of the called routine is the ADDWF PCL instruction. The next instruction executed will be one of the RETLW nn instructions that returns the value ‘nn’ to the calling function if Read Microchip Microcontroller PIC18F4450 Program.
The offset value (in WREG) specifies the number of bytes that the program counter should advance and
should be multiples of 2 (LSb = 0). In this method, only one data byte may be stored in each instruction location and room on the return address stack is required if READ MCU.
