Does this work on your 12F509?
Code:
DEFINE DEBUG_BAUD 9600
DEFINE DEBUGIN_REG GPIO
DEFINE DEBUGIN_BIT 1
DEFINE DEBUGIN_MODE 0 '1=inverted

X 	var 	byte			' dummy variable

' Pin Assignments
SCADAin		var gpio.1		' data in via MAX232
Ready		var gpio.4		' signal main processor to send data

	low ready	' set low

' config
	TRISIO = %000010		' set I/O directions (0 = output, 1 = input)
	OPTION_REG = %11011111	' 12F508/9  bit 6 disables weak pull-ups

Main:
	debugin 200,NoOp,[wait($0F)]	' wait for address and command

	pause 10		' wait for serial burst to end
	high Ready	' signal main processor to send current data
	pause 2		' with a 2mS pulse
	low ready

	goto main
	
NoOp:
	GOTO Main
	
	END