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00066_MCP402XEV.ASM Source Code

;**********************************************************************************************

; General Pupose Register Definitions

;**********************************************************************************************

GPRS UDATA

State res 1 ; variable to track the “state” value

; this code functions as a state machine

; bits 3:0 stores the state 0-15 indicator

; bits 7:6 stores the debounced button states

OldState res 1 ; allows program to see if State changed

Exit res 1 ; variable to count the number ms to test for a button press

DebounceUP res 1 ; variable to count the number of ms UP was pressed

DebounceDOWN res 1 ; variable to count the number of ms DOWN was pressed

DLYCNT1 res 1 ; variable for the delay subroutines

DLYCNT2 res 1 ; variable for the delay subroutines

#define UD GPIO,1 ; GP1 tied to UD & has “INCR” switch connected via 2.2k resistor

#define CS GPIO,0 ; GP0 tied to CS & has “DECR” switch connected via 2.2k resistor

#define UP GPIO,1 ; Momentary switch UP

#define DOWN GPIO,0 ; Momentary switch DOWN

#define CP GPIO,2 ; OSCOUT pin for Charge Pump

#define PowerDown GPIO,3 ; Vpp for programming & PowerDown input to put uC to SLEEP

#define HV_CS OSCCAL,FOSC4 ; Drives CS to HVDD (drive CS high first)

#define UP_State State,7 ; Debounced UP State - using bits 5:4 are critical

#define DOWN_State State,6 ; Debounced DOWN State - using bits 5:4 are critical

;***********************************************************************************************

; Reset Code

;***********************************************************************************************

RESET CODE ; processor reset vector + 1

;ResetVector ; Device resets to 0x1FF to get the factory calibration

goto Start ; Lower half of memory reserved for subroutines

;***********************************************************************************************

; Main Code

;***********************************************************************************************

MAIN CODE

Start

Init_Oscillator

; Internal RC calibration value is placed at location 0xFF by Microchip

; as a movlw k, where the k is a literal value.

movwf OSCCAL ; update register with factory cal value

; bcf OSCCAL,FOSC4 ; make sure the FOSC4 is disabled to shut charge pump off

StateMachineReset

movlw b’11110011’ ; Disable the Comparator & make inputs digital

movwf CMCON0

; bcf CMCON0, CMPON ; needs to be on to get GP2 as a General Purpose Output

movlw b’10011010’ ; disable Wake-Up on Pin Change,

; enable weak pullups for button inputs

; T0CS must be 0 for GP2 TRIS to be active

; set up for 72ms WDT

option

Init

clrf State

clrf OldState

call InitGPIO ; make GP0/DECR/CS & GP1/INCR/UD outputs, block undesired U/D commands

TABLE E-1: 00066_MCP402XEV.ASM SOURCE CODE (CONTINUED)