LCD serial interrupt initialization and ISR routine

Serial_ISR.pbp

;Enable unmasked peripheral interrupts
INTCON = %11000000

;Declear interrupt handler
ON INTERRUPT goto Serial_Interrupt

;Enable interrupt on USART (Serial Receive)
PIE1.5 = 1

...

;-----[ Variables ]--------------------------------------------------------
;High Baud Rate Select bit
BRGH            VAR         TXSTA.2

;Receive interrupt flag (1 = full, 0 = empty)
RCIF            VAR         PIR1.5

;-----[ EEPROM ]-----------------------------------------------------------

;Reference labels for associated memory locations

;EEPROM locations 0 and 1 store the default baud rate value (9600 baud)
_BRGH            DATA   @0, 0
_SPBRG           DATA   @1, 32

...

;-----[ Initialization ]---------------------------------------------------
Init:

...
    
    ;Read BRGH Baud Rate Select Bit and SPBRG Register from memory.  Set
    ;baud rate based on these values. A better understanding of these 
    ;settings can be gathered from the selected microcontroller data sheet.
    ;GOSUB READ_BAUD_RATE 
    read _BRGH, BRGH
    read _SPBRG, SPBRG

...
    ;We read BRGH and SPBRG values from EEPROM.  BRGH will be 0 for low bit
    ;rates and 1 for high bit rates. The below routine is used to display
    ;the saved baud rate on initial power on of the LCD controller. This is
    ;to aid in pairing the correct baud rate from the controller/PC to the 
    ;LCD controller. A Clear Screen command should be sent to the LCD 
    ;before sending further data unless you want the baud rate to stay on 
    ;the display.
    select case brgh
        case 0
            size = 4
            ARRAYWRITE baud, ["9600"]

        case 1
            select case SPBRG
                case 64
                    size = 5
                    ARRAYWRITE baud, ["19200"]

                case 32
                    size = 5
                    ARRAYWRITE baud, ["38400"]

                case 21
                    size = 5
                    ARRAYWRITE baud, ["57600"]                                        
                    
                case else
            END SELECT
    end select   

...

;--------------------------------------------------------------------------
;Serial Interrupt routine
;--------------------------------------------------------------------------
;Make sure we do interrupt our interrupt
disable
Serial_Interrupt:
    ;Check for serial input
    if (RCIF = 1) then
        
        ;Keep track of serial buffer
        index = index + 1
        
        ;If buffer over-flows reset buffer
        if (index = buffer_size) then index = 0
            
        ;Get serial input and store in array
        hserin [Rx_Array[index]]
    endif
resume
enable