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Scenix Lib IO Dev Modem SIMPLE_FSK_RCV_1_10

; *****************************************************************************************
; Copyright © [01/26/1999] Scenix Semiconductor, Inc. All rights reserved.
;
; Scenix Semiconductor, Inc. assumes no responsibility or liability for
; the use of this [product, application, software, any of these products].
; Scenix Semiconductor conveys no license, implicitly or otherwise, under
; any intellectual property rights.
; Information contained in this publication regarding (e.g.: application,
; implementation) and the like is intended through suggestion only and may
; be superseded by updates. Scenix Semiconductor makes no representation
; or warranties with respect to the accuracy or use of these information,
; or infringement of patents arising from such use or otherwise.
;*****************************************************************************************
; 
; Filename:	simple_fsk_rcv_1_10.src
;
; Authors:	Chris Fogelklou
;		Applications Engineer
;		Scenix, Inc.
;
; Revision:	1.10
;
; Part:		SX28AC datecode 9929AA
;
; Freq:		50Mhz
;
; Compiled using Parallax SX-Key software v1.07 and SASM 1.40
;
; Date Written: January 25, 1999
;
; Last Revised: November 17, 1999
;
; Program Description:	This is simple software to demonstrate the concept of 
;			converting an incoming frequency to a data train.  This 
;			program simply watches the incoming frequency and outputs
;			a high or a low to the RS-232 TX pin.  For this reason, the
;			PC that the board is connected to must be set to the desired
;			baud rate.  Example:  If a 300,N,8,1 settings are desired, 
;			simply set the PC's terminal program to these settings and
;			the SX modem will act as a simple frequency-voltage converter,
;			translating the incoming frequency (1300Hz and 2100Hz) to 
;			an output voltage which the computer will receive as a 300,N,8,1
;			data packet.  Once the modem is connected, simply press a key
;			on the keyboard to get it to pick up and begin receiving.
;
;			Disclaimer:  	This program is simplified...  It is just
;					for demo purposes, to show the power and 
;					simplicity of Virtual Peripherals for telephony
;					applications.  An actual modem would need a 
;					more complex algorithm (See the V.23 Modem Appnote)
;					to achieve sufficient error response.
;
;			Note:		This program works only with an accurate Oscillator.
;					The SX-ISD's Oscillator is not accurate enough to
;					produce error-free results.  The XTAL on the Scenix
;					Demo boards produced better results.
;
;	INPUTS:
;	FSK input on fsk_rx_pin (rb.1) (Signal must be passed through comparator/zero-cross
;					circuitry.)
;	RS-232 input on rx_pin (ra.1)
;
;	OUTPUTS:
;	Received RS-232 characters on tx_pin (ra.2)
;	LED flashes while receiving on led_pin (rb.0)
;
; Revision History:  	1.0  Drew out the FSK receive code from the rest of the code
;		 	surrounding it in the old modem demo software and implemented
;			it as a module by itself (December 17, 1998)
;			1.01 Added more documentation to the software for web-posting.
;			(January 25, 1999)
;			1.02 Added support for rev 1.4 boards (2/23/99)
;			1.10 Updated the program for the SASM assembler
;
;	RESOURCES:
;       Program memory: 91 Words
;       Data memory:	2 1/8 bytes
;*****************************************************************************************

;*****************************************************************************************
; Target SX
; Uncomment one of the following lines to choose the SX18AC, SX20AC, SX28AC, SX48BD/ES,
; SX48BD, SX52BD/ES or SX52BD. For SX48BD/ES and SX52BD/ES, uncomment both defines,
; SX48_52 and SX48_52_ES.
;*****************************************************************************************
;SX18_20
SX28
;SX48_52
;SX48_52_ES

;*****************************************************************************************
; Assembler Used
; Uncomment the following line if using the Parallax SX-Key assembler. SASM assembler
; enabled by default.
;*****************************************************************************************
SX_Key

	;*********************************************************************************
	; Assembler directives:
	;	high speed external osc, turbo mode, 8-level stack, and extended option reg.
	;
	;	SX18/20/28 - 4 pages of program memory and 8 banks of RAM enabled by default.
	;	SX48/52 - 8 pages of program memory and 16 banks of RAM enabled by default.
	;                
	;*********************************************************************************

IFDEF SX_Key 				;SX-Key Directives
  IFDEF SX18_20				;SX18AC or SX20AC device directives for SX-Key
		device	SX18L,oschs2,turbo,stackx_optionx
  ENDIF
  IFDEF SX28				;SX28AC device directives for SX-Key		
		device	SX28L,oschs2,turbo,stackx_optionx
  ENDIF
  IFDEF SX48_52_ES			;SX48BD/ES or SX52BD/ES device directives for SX-Key
		device	oschs,turbo,stackx,optionx
  ELSE
    IFDEF SX48_52				;SX48/52/BD device directives for SX-Key
		device	oschs2
    ENDIF
  ENDIF
		freq	50_000_000
ELSE  					;SASM Directives
  IFDEF SX18_20				;SX18AC or SX20AC device directives for SASM
		device	SX18,oschs2,turbo,stackx,optionx
  ENDIF
  IFDEF SX28				;SX28AC device directives for SASM
		device	SX28,oschs2,turbo,stackx,optionx
  ENDIF
  IFDEF SX48_52_ES			;SX48BD/ES or SX52BD/ES device directives for SASM
		device	SX52,oschs,turbo,stackx,optionx
  ELSE
    IFDEF SX48_52			;SX48BD or SX52BD device directives for SASM
		device	SX52,oschs2  
    ENDIF
  ENDIF
ENDIF
		id	'SFSKRX11'			;
		reset	reset_entry		; set reset vector

;*****************************************************************************************
; Macros
;*****************************************************************************************

	;*********************************************************************************
	; Macro: _bank
	; Sets the bank appropriately for all revisions of SX.
	;
	; This is required since the bank instruction has only a 3-bit operand, it cannot
	; be used to access all 16 banks of the SX48/52. For this reason FSR.4 (for SX48/52BD/ES)
	; or FSR.7 (SX48/52bd production release) needs to be set appropriately, depending
	; on the bank address being accessed. This macro fixes this.
	;
	; So, instead of using the bank instruction to switch between banks, use _bank instead.
	; 
	;*********************************************************************************
_bank	macro	1
	bank	\1

	IFDEF SX48_52
	  IFDEF SX48_52_ES
	    IF \1 & %00010000		;SX48BD/ES and SX52BD/ES (engineering sample) bank instruction
		setb	fsr.4		;modifies FSR bits 5,6 and 7. FSR.4 needs to be set by software.
	    ENDIF
	  ELSE
	    IF \1 & %10000000		;SX48BD and SX52BD (production release) bank instruction 
		setb	fsr.7		;modifies FSR bits 4,5 and 6. FSR.7 needs to be set by software.
	    ELSE
		clrb	fsr.7
	    ENDIF
	  ENDIF
	ENDIF
	endm

	;*********************************************************************************
	; Macro: _mode
	; Sets the MODE register appropriately for all revisions of SX.
	;
	; This is required since the MODE (or MOV M,#) instruction has only a 4-bit operand. 
	; The SX18/20/28AC use only 4 bits of the MODE register, however the SX48/52BD have 
	; the added ability of reading or writing some of the MODE registers, and therefore use
	; 5-bits of the MODE register. The  MOV M,W instruction modifies all 8-bits of the 
	; MODE register, so this instruction must be used on the SX48/52BD to make sure the MODE
	; register is written with the correct value. This macro fixes this.
	;
	; So, instead of using the MODE or MOV M,# instructions to load the M register, use
	;  _mode instead.
	; 
	;*********************************************************************************
_mode	macro	1
	IFDEF SX48_52
		mov	w,#\1		;loads the M register correctly for the SX48BD and SX52BD
		mov	m,w
	ELSE
		mov	m,#\1		;loads the M register correctly for the SX18AC, SX20AC
					;and SX28AC
	ENDIF
	endm

;*****************************************************************************************
; Data Memory address definitions
; These definitions ensure the proper address is used for banks 0 - 7 for 2K SX devices
; (SX18/20/28) and 4K SX devices (SX48/52). 
;*****************************************************************************************
IFDEF SX48_52

global_org	=	$0A
bank0_org	=	$00
bank1_org	=	$10
bank2_org	=	$20
bank3_org	=	$30
bank4_org	=	$40
bank5_org	=	$50
bank6_org	=	$60
bank7_org	=	$70

ELSE

global_org	=	$08
bank0_org	=	$10
bank1_org	=	$30
bank2_org	=	$50
bank3_org	=	$70
bank4_org	=	$90
bank5_org	=	$B0
bank6_org	=	$D0
bank7_org	=	$F0

ENDIF
;*****************************************************************************************
; Global Register definitions
; NOTE: Global data memory starts at $0A on SX48/52 and $08 on SX18/20/28.
;*****************************************************************************************
		org     global_org

function_temp	equ	global_org+1
global_temp	equ	global_org+2


;*****************************************************************************************
; RAM Bank Register definitions
;*****************************************************************************************

	;*********************************************************************************
	; Bank 0
	;*********************************************************************************
		org     bank0_org

bank0		=	$

flags			ds	1
	fsk_rx_en	equ	flags.0 ; Enables the FSK receiver.

	;*********************************************************************************
	; Bank 1
	;*********************************************************************************
		org     bank1_org

bank1		=	$

fsk_receive_bank	=	$

	fsk_trans_count	ds	1		; This register counts the number of counts 
						; between transitions at the pin
	rb_past_state	ds	1		; This register keeps track of the previous 
						; state of port RB, to watch for transitions

	;*********************************************************************************
	; Bank 2
	;*********************************************************************************
		org     bank2_org

bank2		=	$


	;*********************************************************************************
	; Bank 3
	;*********************************************************************************
		org     bank3_org

bank3		=	$


	;*********************************************************************************
	; Bank 4
	;*********************************************************************************
		org     bank4_org

bank4		=	$


	;*********************************************************************************
	; Bank 5
	;*********************************************************************************
		org     bank5_org

bank5		=	$


	;*********************************************************************************
	; Bank 6
	;*********************************************************************************
		org     bank6_org

bank6		=	$


	;*********************************************************************************
	; Bank 7
	;*********************************************************************************
		org     bank7_org

bank7		=	$


IFDEF SX48_52
	;*********************************************************************************
	; Bank 8
	;*********************************************************************************
		org	$80	;bank 8 address on SX52

bank8		=	$


	;*********************************************************************************
	; Bank 9
	;*********************************************************************************
		org	$90	;bank 9 address on SX52

bank9		=	$


	;*********************************************************************************
	; Bank A
	;*********************************************************************************
		org	$A0	;bank A address on SX52

bankA		=	$


	;*********************************************************************************
	; Bank B
	;*********************************************************************************
		org	$B0	;bank B address on SX52

bankB		=	$


	;*********************************************************************************
	; Bank C
	;*********************************************************************************
		org	$C0	;bank C address on SX52

bankC		=	$


	;*********************************************************************************
	; Bank D
	;*********************************************************************************
		org	$D0	;bank D address on SX52

bankD		=	$


	;*********************************************************************************
	; Bank E
	;*********************************************************************************
		org	$E0	;bank E address on SX52

bankE		=	$


	;*********************************************************************************
	; Bank F
	;*********************************************************************************
		org	$F0	;bank F address on SX52

bankF		=	$


ENDIF

;*********************************************************************************
; Pin Definitions	(These pins are for use with the Scenix Modem Demo Board,
;			 Rev. 1.2)
;*********************************************************************************
PDM_pin		equ	ra.0	; D/A output pin
rx_pin		equ	ra.1	; RS-232 reception pin
tx_pin		equ	ra.2	; RS-232 transmission pin
nothing		equ	ra.3	; N/C
RA_latch	equ	%11111111		;SX18/20/28/48/52 port A latch init
RA_DDIR		equ	%11111011		;SX18/20/28/48/52 port A DDIR value
RA_LVL		equ	%00000000		;SX18/20/28/48/52 port A LVL value
RA_PLP		equ	%11111111		;SX18/20/28/48/52 port A PLP value

led_pin		equ	rb.0	; LED pin
rxa_pin		equ	rb.1	; FSK receive pin
cntrl_1		equ	rb.2	; drive cntrl_1 low to disable the output of the LPF
ring		equ	rb.3	; ring detection pin
hook		equ	rb.4	; drive hook low to go off-hook
cntrl_3		equ	rb.5	; drive cntrl_3 low to disable the output of the HPF
rts		equ	rb.6	; indicates to the SX that the PC wants to transmit data
cts		equ	rb.7	; indicates to the PC that the SX is ready to receive data
RB_latch	equ	%11011011		;SX18/20/28/48/52 port B latch init
RB_DDIR		equ	%01101010		;SX18/20/28/48/52 port B DDIR value
RB_ST		equ	%11111111		;SX18/20/28/48/52 port B ST value
RB_LVL		equ	%00000000		;SX18/20/28/48/52 port B LVL value
RB_PLP		equ	%11111111		;SX18/20/28/48/52 port B PLP value

dtmf_in_pin	equ	rc.0	; DTMF input pin
dtmf_fdbk_pin	equ	rc.1	; Negative feedback output for DTMF input
AtoD_in_pin	equ	rc.2	; A/D input pin
AtoD_fdbk_pin	equ	rc.3	; Negative feedback for A/D input
imp_450_pin	equ	rc.4	; Set to an output to set hybrid for 450ohm line impedance.  Tristate otherwise.
imp_600_pin	equ	rc.5	; Set to an output to set hybrid for 600ohm line impedance.  Tristate otherwise.
imp_750_pin	equ	rc.6	; Set to an output to set hybrid for 750ohm line impedance.  Tristate otherwise.
imp_900_pin	equ	rc.7	; Set to an output to set hybrid for 900ohm line impedance.  Tristate otherwise.
RC_latch	equ	%00001111		;SX18/20/28/48/52 port C latch init
RC_DDIR		equ	%11010101		;SX18/20/28/48/52 port C DDIR value
RC_ST		equ	%11111111		;SX18/20/28/48/52 port C ST value
RC_LVL		equ	%00000000		;SX18/20/28/48/52 port C LVL value
RC_PLP		equ	%11111111		;SX18/20/28/48/52 port C PLP value

IFDEF SX48_52	;SX48BD/52BD Port initialization values
RD_latch	equ	%00000000		;SX48/52 port D latch init
RD_DDIR		equ	%11111111		;SX48/52 port D DDIR value
RD_ST		equ	%11111111		;SX48/52 port D ST value
RD_LVL		equ	%00000000		;SX48/52 port D LVL value
RD_PLP		equ	%11111111		;SX48/52 port D PLP value

RE_latch	equ	%00000000		;SX48/52 port E latch init
RE_DDIR		equ	%11111111		;SX48/52 port E DDIR value
RE_ST		equ	%11111111		;SX48/52 port E ST value
RE_LVL		equ	%00000000		;SX48/52 port E LVL value
RE_PLP		equ	%11111111		;SX48/52 port E PLP value
ENDIF


;*****************************************************************************************
; Program constants
;*****************************************************************************************
;******************************************************************************
; Equates for FSK reception
;******************************************************************************
glitch_th		equ	20	; The threshold which defines a glitch (small spike which should be ignored)
low_count_error_th	equ	40	; The lowest count allowed for a high frequency
low_high_th		equ	95	; The lowest count allowed for a low frequency
high_count_error_th	equ	140	; The highest count allowed for a low frequency


int_period	equ	163		;RTCC Interrupt rate

IFDEF SX48_52
	;*********************************************************************************
	; SX48BD/52BD Mode addresses
	; *On SX48BD/52BD, most registers addressed via mode are read and write, with the
	; exception of CMP and WKPND which do an exchange with W.
	;*********************************************************************************
; Timer (read) addresses
TCPL_R		equ	$02		;Read Timer Capture register low byte
TCPH_R		equ	$02		;Read Timer Capture register high byte
TR2CML_R	equ	$02		;Read Timer R2 low byte
TR2CMH_R	equ	$03		;Read Timer R2 high byte
TR1CML_R	equ	$04		;Read Timer R1 low byte
TR1CMH_R	equ	$05 		;Read Timer R1 high byte
TCNTB_R		equ	$06		;Read Timer control register B
TCNTA_R		equ	$07		;Read Timer control register A

; Exchange addresses
CMP		equ	$08		;Exchange Comparator enable/status register with W
WKPND		equ	$09		;Exchange MIWU/RB Interrupts pending with W

; Port setup (read) addresses
WKED_R		equ	$0A		;Read MIWU/RB Interrupt edge setup, 0 = falling, 1 = rising
WKEN_R		equ	$0B		;Read MIWU/RB Interrupt edge setup, 0 = enabled, 1 = disabled
ST_R		equ	$0C		;Read Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
LVL_R		equ	$0D		;Read Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
PLP_R		equ	$0E		;Read Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
DDIR_R		equ	$0F		;Read Port Direction

; Timer (write) addresses
TR2CML_W	equ	$12		;Write Timer R2 low byte
TR2CMH_W	equ	$13		;Write Timer R2 high byte
TR1CML_W	equ	$14		;Write Timer R1 low byte
TR1CMH_W	equ	$15 		;Write Timer R1 high byte
TCNTB_W		equ	$16		;Write Timer control register B
TCNTA_W		equ	$17		;Write Timer control register A

; Port setup (write) addresses
WKED_W		equ	$1A		;Write MIWU/RB Interrupt edge setup, 0 = falling, 1 = rising
WKEN_W		equ	$1B		;Write MIWU/RB Interrupt edge setup, 0 = enabled, 1 = disabled
ST_W		equ	$1C		;Write Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
LVL_W		equ	$1D		;Write Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
PLP_W		equ	$1E		;Write Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
DDIR_W		equ	$1F		;Write Port Direction

ELSE

	;*********************************************************************************
	; SX18AC/20AC/28AC Mode addresses
	; *On SX18/20/28, all registers addressed via mode are write only, with the exception of
	; CMP and WKPND which do an exchange with W.
	;*********************************************************************************
; Exchange addresses
CMP		equ	$08		;Exchange Comparator enable/status register with W
WKPND		equ	$09		;Exchange MIWU/RB Interrupts pending with W

; Port setup (read) addresses
WKED_W		equ	$0A		;Write MIWU/RB Interrupt edge setup, 0 = falling, 1 = rising
WKEN_W		equ	$0B		;Write MIWU/RB Interrupt edge setup, 0 = enabled, 1 = disabled
ST_W		equ	$0C		;Write Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
LVL_W		equ	$0D		;Write Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
PLP_W		equ	$0E		;Write Port Schmitt Trigger setup, 0 = enabled, 1 = disabled
DDIR_W		equ	$0F		;Write Port Direction
ENDIF

;*****************************************************************************************
; Interrupt Service Routine
;*****************************************************************************************
; Note: The interrupt code must always originate at address $0.
;
; Interrupt Frequency = (Cycle Frequency / -(retiw value))  For example:
; With a retiw value of -163 and an oscillator frequency of 50MHz, this
; code runs every 3.26us.
;*****************************************************************************************
		org     $0
interrupt					;3

	;*********************************************************************************
	; Virtual Peripheral: FSK Detection (Simple)
	;
	;
	;	Input variable(s):  	fsk_rx_en:  Enables/Disables this routine
	;				RB.1:	FSK Input on this port pin.
	;	Output variable(s): 	Sets/Clears the LED_pin and the tx_pin, depending on
	;				the current input frequency
	;	Variable(s) affected: 	fsk_trans_count, rb_past_state
	;	Flag(s) affected: 	None
	;	Variable Length?:	Yes.
	;*********************************************************************************
		jnb	fsk_rx_en,fsk_rx_out	; jump out if the FSK receiver is not enabled

FSK_RECEIVE
		bank	fsk_receive_bank	; switch to fsk_receive_bank of RAM

		add	fsk_trans_count,#1	; Regardless of what is going on, increment the 
		snc				; transition timer.  These get cleared when a transition 
		jmp	:error			; takes place.

		cjb	fsk_trans_count,#low_high_th,:fsk_timer_out	; as soon as it takes longer than 95 counts
		setb	tx_pin						; to transition, this must be a low frequency
		clrb	LED_pin						; If a high is being sent, clear the LED
		
:fsk_timer_out

		mov	w,rb
		and	w,#%00000010		; get the current state of rb.
		xor	w,rb_past_state		; compare it with the previous state of the pin
		jz	fsk_rx_out		; if there was no change, then jump out, there is nothing to do.
		
						; Now it is time to determine if the transition that took place indicates a bit was received
						; (it must be within some thresholds... below 20, ignore it, below 40, what???,
						; below 95, high frequency, below 140, low frequency (already set), above 140,
						; what???)

		cjb	fsk_trans_count,#glitch_th,:glitch_so_ignore		; pulse was below specs, ignore it... probably noise
		cjb	fsk_trans_count,#low_count_error_th,:error		; pulse was not a glitch but wasn't long enough to mean anything... huh?
		cjb	fsk_trans_count,#low_high_th,:high_frequency		; pulse was within specs for a high frequency...
		cjb	fsk_trans_count,#high_count_error_th,:fsk_receive_done	; pulse was within specs for a low frequency (don't do anything)
		jmp	:error							; pulse was too long to mean anything, so do nothing.
		
:high_frequency						; a high frequency corresponds to low data.
		clrb	tx_pin
		setb	LED_pin				; set the LED to indicate a LOW is being sent.
		jmp	:fsk_receive_done

:error
;--------------- PUT ERROR HANDLING CODE IN HERE -----------------

:fsk_receive_done			
		clr	fsk_trans_count			; clear the bit counter.
:glitch_so_ignore					; don't clear the counter if the data was a glitch
		mov	w,rb				; save the new state of RB.
		and	w,#%00000010
		mov	rb_past_state,w
fsk_rx_out

	;*********************************************************************************
	; Set Interrupt Rate
	;*********************************************************************************
isr_end		mov	w,#-int_period		;refresh RTCC on return
		retiw				;return from the interrupt
						; = 1/(int_period*RTCC prescaler*1/50MHz)
						; = 1/(163*1*20ns) = 1/3.26us = 306.7kHz
;*****************************************************************************************
; End of the Interrupt Service Routine
;*****************************************************************************************

;*****************************************************************************************
; RESET VECTOR 
;*****************************************************************************************

	;*********************************************************************************
	; Program execution begins here on power-up or after a reset
	;*********************************************************************************
reset_entry	jmp	@_reset_entry	; Go to the location in the last page where the
					; main program is.



;*****************************************************************************************
org	$200
;*****************************************************************************************
; Jump table for page 1
; Enables CALLs to functions in the second half of the page 
;*****************************************************************************************
;function_label_2	jmp	function_label_2_

;*****************************************************************************************
; Subroutines
;*****************************************************************************************

	;*********************************************************************************
	; Function: 
	; 
	; Inputs:
	;	
	; Outputs:
	;	
	; Registers affected:
	;
	; Functions Called:
	;
	;*********************************************************************************
;function_label

;		retp

	;*********************************************************************************
	; Function: 
	; 
	; Inputs:
	;	
	; Outputs:
	;	
	; Registers affected:
	;
	; Functions Called:
	;
	;*********************************************************************************
;function_label_1

;		retp

	;*********************************************************************************
	; Function: 
	; 
	; Inputs:
	;	
	; Outputs:
	;	
	; Registers affected:
	;
	; Functions Called:
	;
	;*********************************************************************************
;function_label_2_

;		retp

;*****************************************************************************************
org	$400
;*****************************************************************************************
;*****************************************************************************************
org	$600
;*****************************************************************************************
;*****************************************************************************************
; RESET VECTOR 
;*****************************************************************************************

	;*********************************************************************************
	; Program execution begins here on power-up or after a reset
	;*********************************************************************************
_reset_entry
	;*********************************************************************************
	; Initialise all port configuration
	;*********************************************************************************

		_mode	ST_W			;point MODE to write ST register
		mov     w,#RB_ST            	;Setup RB Schmitt Trigger, 0 = enabled, 1 = disabled
		mov	!rb,w		
		mov     w,#RC_ST            	;Setup RC Schmitt Trigger, 0 = enabled, 1 = disabled
		mov	!rc,w	
IFDEF SX48_52
		mov     w,#RD_ST            	;Setup RD Schmitt Trigger, 0 = enabled, 1 = disabled
		mov	!rd,w		
		mov     w,#RE_ST            	;Setup RE Schmitt Trigger, 0 = enabled, 1 = disabled
		mov	!re,w		
ENDIF
		_mode	LVL_W			;point MODE to write LVL register
		mov     w,#RA_LVL            	;Setup RA CMOS or TTL levels, 0 = TTL, 1 = CMOS
		mov	!ra,w		 
		mov     w,#RB_LVL            	;Setup RB CMOS or TTL levels, 0 = TTL, 1 = CMOS
		mov	!rb,w		
		mov     w,#RC_LVL            	;Setup RC CMOS or TTL levels, 0 = TTL, 1 = CMOS
		mov	!rc,w	
IFDEF SX48_52
		mov     w,#RD_LVL            	;Setup RD CMOS or TTL levels, 0 = TTL, 1 = CMOS
		mov	!rd,w		
		mov     w,#RE_LVL            	;Setup RE CMOS or TTL levels, 0 = TTL, 1 = CMOS
		mov	!re,w		
ENDIF
		_mode	PLP_W			;point MODE to write PLP register
		mov     w,#RA_PLP            	;Setup RA Weak Pull-up, 0 = enabled, 1 = disabled
		mov	!ra,w		 
		mov     w,#RB_PLP            	;Setup RB Weak Pull-up, 0 = enabled, 1 = disabled
		mov	!rb,w		
		mov     w,#RC_PLP            	;Setup RC Weak Pull-up, 0 = enabled, 1 = disabled
		mov	!rc,w	
IFDEF SX48_52
		mov     w,#RD_PLP            	;Setup RD Weak Pull-up, 0 = enabled, 1 = disabled
		mov	!rd,w		
		mov     w,#RE_PLP            	;Setup RE Weak Pull-up, 0 = enabled, 1 = disabled
		mov	!re,w		
ENDIF
		_mode	DDIR_W			;point MODE to write DDIR register
		mov	w,#RA_DDIR		;Setup RA Direction register, 0 = output, 1 = input		
		mov	!ra,w	
		mov	w,#RB_DDIR		;Setup RB Direction register, 0 = output, 1 = input
		mov	!rb,w			
		mov	w,#RC_DDIR		;Setup RC Direction register, 0 = output, 1 = input
		mov	!rc,w			
IFDEF SX48_52
		mov	w,#RD_DDIR		;Setup RD Direction register, 0 = output, 1 = input
		mov	!rd,w			
		mov	w,#RE_DDIR		;Setup RE Direction register, 0 = output, 1 = input
		mov	!re,w			
ENDIF
		mov     w,#RA_latch          	;Initialize RA data latch
		mov     ra,w		
		mov     w,#RB_latch         	;Initialize RB data latch
		mov     rb,w		
		mov     w,#RC_latch          	;Initialize RC data latch
		mov     rc,w		
IFDEF SX48_52
		mov     w,#RD_latch         	;Initialize RD data latch
		mov     rd,w			
		mov     w,#RE_latch         	;Initialize RE data latch
		mov     re,w			
ENDIF


	;*********************************************************************************
	; Clear all Data RAM locations
	;*********************************************************************************
IFDEF SX48_52   				;SX48/52 RAM clear routine
		mov	w,#$0a			;reset all ram starting at $0A
		mov	fsr,w
:zero_ram	clr	ind			;clear using indirect addressing
		incsz	fsr			;repeat until done
		jmp	:zero_ram

		_bank	bank0			;clear bank 0 registers
		clr	$10
		clr	$11
		clr	$12
		clr	$13
		clr	$14
		clr	$15
		clr	$16
		clr	$17
		clr	$18
		clr	$19
		clr	$1a
		clr	$1b
		clr	$1c
		clr	$1d
		clr	$1e
		clr	$1f

ELSE     					;SX18/20/28 RAM clear routine
		clr	fsr			;reset all ram banks
:zero_ram	sb	fsr.4			;are we on low half of bank?
		setb	fsr.3			;If so, don't touch regs 0-7
		clr	ind			;clear using indirect addressing
		incsz	fsr			;repeat until done
		jmp	:zero_ram
ENDIF
	;*********************************************************************************
	; Initialize program/VP registers
	;*********************************************************************************


	;*********************************************************************************
	; Setup and enable RTCC interrupt, WREG register, RTCC/WDT prescaler
	;*********************************************************************************

RTCC_ON		=	%10000000	;Enables RTCC at address $01 (RTW hi)
					;*WREG at address $01 (RTW lo) by default
RTCC_ID		=	%01000000	;Disables RTCC edge interrupt (RTE_IE hi)
					;*RTCC edge interrupt (RTE_IE lo) enabled by default
RTCC_INC_EXT	=	%00100000	;Sets RTCC increment on RTCC pin transition (RTS hi)
					;*RTCC increment on internal instruction (RTS lo) is default
RTCC_FE		=	%00010000	;Sets RTCC to increment on falling edge (RTE_ES hi)
					;*RTCC to increment on rising edge (RTE_ES lo) is default
RTCC_PS_ON	=	%00000000	;Assigns prescaler to RTCC (PSA lo)
RTCC_PS_OFF	=	%00001000	;Assigns prescaler to RTCC (PSA lo)
PS_000		=	%00000000	;RTCC = 1:2, WDT = 1:1
PS_001		=	%00000001	;RTCC = 1:4, WDT = 1:2
PS_010		=	%00000010	;RTCC = 1:8, WDT = 1:4
PS_011		=	%00000011	;RTCC = 1:16, WDT = 1:8
PS_100		=	%00000100	;RTCC = 1:32, WDT = 1:16
PS_101		=	%00000101	;RTCC = 1:64, WDT = 1:32
PS_110		=	%00000110	;RTCC = 1:128, WDT = 1:64
PS_111		=	%00000111	;RTCC = 1:256, WDT = 1:128

		mov	w,#RTCC_PS_OFF	;setup option register
		mov	!option,w
		jmp	@main

;*****************************************************************************************
; MAIN PROGRAM CODE 
;*****************************************************************************************

	;*********************************************************************************
	; Main
	;*********************************************************************************
main		
		clrb	CTS
		jb	rx_pin,$		; until the user presses a key, loop indefinetely

		
		clrb	hook			; pick up the line
		setb	fsk_rx_en		; enable the FSK receiver

	;*********************************************************************************
	; Main Program Loop
	;*********************************************************************************
main_loop
		
		; Do nothing...  ISR Does everything.

		jmp	main_loop


;*****************************************************************************************
END		;End of program code
;*****************************************************************************************


file: /Techref/scenix/lib/io/dev/modem/simple_fsk_rcv_1_10.SRC, 32KB, , updated: 2002/4/11 13:05, local time: 2017/10/18 22:25,
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