; MICROCHIP KEELOQ CODE HOPPING SIMPLE DECODER
;
; 一步學習； 單一鍵
;www.nbglin.com 電話：0574-88464538
;歌林電子制作工作室
; 配置控制:
; -VERSION 1.1 S. DAWSON
;
; FILE: SIMDEC11.ASM. 
; DATE: 8 SEPTEMBER 1998 
; VER.: 1.1
; FUSES: RC,WDT=ON,CP=ON.
; ASM.: MPASM VERSION 2.13 USED.
; INCL: NONE
;
;---------------------------------------------
LIST P=16C54,R=DEC
;---------------------------------------------

MAX_USERS EQU 15
; 這是系統的最大數，因此系統能記住(1 to 15). 
;---------------------------------------------
IND EQU 00H 
RTCC EQU 01H 
PC EQU 02H 
STATUS EQU 03H 
FSR EQU 04H 
PORTA EQU 05H 
PORTB EQU 06H 
;----------------------
FLAGS EQU 07H 
ADDRESS EQU 08H 
TXNUM EQU 09H 
OUTBYT EQU 0AH 
MASK EQU OUTBYT 
TMP_CNT EQU OUTBYT 

CNT0 EQU 0BH ; ;計數 
CNT1 EQU 0CH 
CNT2 EQU 0DH 

CNT_HI EQU 0EH ; 16位時鐘
CNT_LW EQU 0FH 

CSR0 EQU 10H ; 64 位接收移位寄存器
CSR1 EQU 11H 
CSR2 EQU 12H 
CSR3 EQU 13H 
CSR4 EQU 14H 
CSR5 EQU 15H 
CSR6 EQU 16H 
CSR7 EQU 17H 

TMP1 EQU 18H 
TMP2 EQU 19H 
REG EQU 1AH ; 
REG1 EQU 1BH ; 臨時寄存器
;
KEY0 EQU 1CH ; 64 BIT KEY SHIFT REGISTER
KEY1 EQU 1DH
KEY2 EQU 1EH
KEY3 EQU 1FH
KEY4 EQU CNT2
KEY5 EQU CSR5
KEY6 EQU CSR6
KEY7 EQU CSR7
;
HOP1 EQU CSR0 ; 32 BIT 
HOP2 EQU CSR1
HOP3 EQU CSR2
HOP4 EQU CSR3
; 
SER_0 EQU CSR7 ; 28 BIT 串行數
SER_1 EQU CSR6
SER_2 EQU CSR5
SER_3 EQU CSR4

; RECEIVED TRANSMISSION ENCRYPTED 32 BITS 

FUNC EQU CSR3 ; BUTTON CODE & USER BIT FUNCTION BYTE
DISC EQU CSR2 ; DISCRIMINATION VALUE
CNTR_HI EQU CSR1 ; 16 BIT RX COUNTER HIGH BYTE
CNTR_LW EQU CSR0 ; 16 BIT RX COUNTER LOW BYTE

; ********* EEPROM MEMORY *******
LRNPTR EQU 01H ; LEARN POINTER

; ********* PORTA BIT DEFINITIONS *******

RES0 EQU 0H ; RESERVED PIN
RFIN EQU 1H ; RF INPUT
LRN EQU 2H ; LEARN BUTTON
LED EQU 3H ; LEARN INDICATOR LED OUTPUT - VALID SIGNAL

; ********* PORTB BIT DEFINITIONS *******

S0 EQU 0H ; S0 OUTPUT
S1 EQU 1H ; S1 OUTPUT
S2 EQU 2H ; S2 OUTPUT
S3 EQU 3H ; S3 OUTPUT

DIO EQU 4H ; EEPROM DATA LINE
CLK EQU 5H ; EEPROM SERIAL CLOCK
CS EQU 6H ; EEPROM CHIP SELECT
RES1 EQU 7H ; RESERVED PIN

; ********* COMPILER DEFINES ******************
NBITS EQU 64 ; MAXIMUM TRANSMISSION BIT LENGTH
MIN EQU 560 ; TRANSMISSION HEADER MINIMUM LENGTH [鍿]
TRISA EQU 0111B ; PORTA: TRI-STATE VALUE
WRCFG EQU 00000000B ; PORTB: EEPROM WRITE TRI-STATE VALUE
RDCFG EQU 00010000B ; PORTB: EEPROM READ TRI-STATE VALUE

;****** FLAGS DEFINITIONS **************
BITIN EQU 0H ; RF BIT VALUE 
LRNF EQU 1H ; LEARN FLAG
SEC_CNT EQU 2H ; SECOND COUNTER IS BEING CHECKED
RELEARN EQU 3H ; RELEARNING A TRANSMITTER

;----------------- STATUS -------------------
C EQU 0 ; CARRY
DC EQU 1 ; DIGIT CARRY
Z EQU 2 ; ZERO
PD EQU 3 ; POWER DOWN
TO EQU 4 ; TIMEOUT
PA0 EQU 5 ; NOT USED
PA1 EQU 6 ; NOT USED 


ORG 00H
;=========================================

RESET 
MOVLW 000111B ; SETUP RTCC PRESCALER
OPTION

CLRF PORTA ; RESET PORTA
CLRF PORTB ; RESET PORTB

MOVLW TRISA ; SETUP PORTA
TRIS PORTA
MOVLW WRCFG ; SETUP PORTB
TRIS PORTB

CLRF FLAGS ; RESET FLAGS

GOTO M_LOOP ; GOTO MAIN PROGRAM LOOP

;---------------------------------------------------------------------------
;
; FUNCTION : ROT_SHIFT() 
;
; DESCRIPTION : RIGHT ROTATE 64 BIT RECEIVE SHIFT REGISTER
;
; NOTE : THIS ROUTINE MUST BE IN THE LOWER HALF OF THE PAGE
;
;---------------------------------------------------------------------------

ROT_SHIFT
RRF CSR7,F
RRF CSR6,F
RRF CSR5,F 
RRF CSR4,F 
RRF CSR3,F 
RRF CSR2,F 
RRF CSR1,F 
RRF CSR0,F 
RETLW 0

;------------------------------------------------------------------------------
;
; FUNCTION : TX_LOOKUP () 
;
; DESCRIPTION : TRANSMITTER ADDRESS CALCULATION
;
; NOTE : THIS ROUTINE MUST BE IN THE LOWER HALF OF THE PAGE
;
;---------------------------------------------------------------------------

TX_LOOKUP
MOVF TXNUM,W ; USE TRANSMITTER NUMBER TO CALCULATE 
MOVWF ADDRESS ; ADDRESS OF TRANSMITER BLOCK
CLRC ; MULTIPLY BY 4 
RLF ADDRESS,F
RLF ADDRESS,F
MOVLW 04H ; AND ADD 4
ADDWF ADDRESS,F
RETLW 0 ; RETURN

;----------------------------------------------------------------------------
;
; FUNCTION : TST_RTCC () 
;
; DESCRIPTION : UPDATE RTCC COUNTER 
;
; NOTE : THIS ROUTINE MUST BE IN THE LOWER HALF OF THE PAGE
;
;---------------------------------------------------------------------------
TST_RTCC
CLRWDT ; RESET WATCHDOG TIMER
MOVLW TRISA ; UPDATE TRI-STATE REGISTER FOR PORTA
TRIS PORTA

BTFSS RTCC,7 ; TEST FOR 32MS TIMEOUT ON RTCC MSB
RETLW 0 ; ... DO QUICK RETURN TO RECEIVE ROUTINE

; **** INCREASE 16 BIT CLOCK TIMER *******

BCF RTCC,7 ; CLEAR MSB OF RTCC
INCF CNT_LW,F ; INCREASE 16 COUNTER
SKPNZ ; INCREASE UPPER BYTE IF ZERO ( OVERFLOW )
INCF CNT_HI,F
RETLW 0

;------------------------------------------------------------------------------
;
; FUNCTION : TST_TIMER() 
;
; DESCRIPTION : TEST 32MS TIMER AND UPDATE OUTPUTS IF REQUIRED
;
; NOTE : THIS ROUTINE MUST BE IN THE LOWER HALF OF THE PAGE
;
;------------------------------------------------------------------------------

TST_TIMER
; ***** TEST FOR 500 MS TIMEMOUT ON OUTPUTS **********
BTFSS CNT_LW,4 ; TEST FOR 500 MS TIMEOUT
GOTO TST_30 ; ... IF NOT TEST 30S TIMEOUT

MOVLW 0F0H
ANDWF PORTB,F ; DOWN ALL PULSE OUTPUTS 

; ********* TEST FOR 30 S LEARN TIMEOUT *************
TST_30 BTFSS FLAGS,LRNF
GOTO TST_END

BTFSC CNT_HI,2 ; TEST FOR LEARN TIMEOUT
GOTO RESET ; ... IF LEARN TIMEMOUT FORCE SOFT RESET 

TST_END 
RETLW 0H

;------------------------------------------------------------------------------
;
; FUNCTION : SENDC () 
;
; DESCRIPTION : SEND EEPROM COMMAND 
;
; NOTE : THIS ROUTINE MUST BE IN THE LOWER HALF OF THE PAGE
;
;------------------------------------------------------------------------------

SENDC
CLRWDT ; RESET WATCHDOG TIMER

BCF PORTB,CS ; RESET CS STATE
BCF PORTB,CLK ; RESET CLK STATE
BCF PORTB,DIO ; RESET DIO STATE

MOVLW WRCFG
TRIS PORTB ; DIO = OUTPUT
GOTO $+1 ; WAIT FOR OUTPUTS TO SETTLE
BSF PORTB,CS ; SELECT EEPROM
SETC ; START BIT = 1
MOVLW 9D ; START BIT + 8 DATA BITS
MOVWF CNT1

SENDC2
SKPC ; TEST BIT
BCF PORTB,DIO ; WRITE TO DIO
SKPNC ; TEST BIT
BSF PORTB,DIO ; WRITE TO DIO
GOTO $+1 ; WAIT 2 US
RLF OUTBYT,F ; GET NEXT BIT INTO CARRY
BSF PORTB,CLK ; CLOCK HIGH
GOTO $+1 ; WAIT 2 US
GOTO $+1 ; WAIT 2 US
BCF PORTB,CLK ; CLOCK LOW
DECFSZ CNT1,F ; LOOP COUNTER
GOTO SENDC2
BCF PORTB,DIO ; AVOID CONTENTION WITH READ
RETLW 0

;------------------------------------------------------------------------------
;
; FUNCTION : EEWRITE () 
;
; DESCRIPTION : WRITE 16 BIT VALUE TO EEPROM 
;
; NOTE : THIS ROUTINE MUST BE IN THE LOWER HALF OF THE PAGE
;
;------------------------------------------------------------------------------

EEWRITE

; ******* EEPROM WRITE ENABLE ******************

WRITE0 MOVLW 30H ; WRITE ENABLE COMMAND
MOVWF OUTBYT 
CALL SENDC ; SEND COMMAND TO EEPROM
BCF PORTB,CS ; END COMMAND, DESELECT

; ******** WRITE 16-BIT WORD TO EEPROM *********

WRITE1 MOVFW ADDRESS ; GET EEPROM ADDRESS
MOVWF OUTBYT
BSF OUTBYT,6 ; WRITE COMMAND
CALL SENDC ; SEND COMMAND TO EEPROM

MOVLW 16D ; 16 DATA BITS
MOVWF CNT1 

WRITE2
BTFSS TMP1,7 ; TEST MSB OF 16 BIT WORD
BCF PORTB,DIO ; SET DATA BIT
BTFSC TMP1,7 ; ... ELSE 
BSF PORTB,DIO ; CLEAR DATA BIT
GOTO $+1 ; WAIT 2 US
RLF TMP2,F ; SHIFT LO BYTE
BSF PORTB,CLK ; CLOCK HIGH
GOTO $+1 ; WAIT 2 US
RLF TMP1,F ; SHIFT HI BYTE
BCF PORTB,CLK ; CLOCK LOW
DECFSZ CNT1,F
GOTO WRITE2 ; LOOP COUNTER

WAITACK
BCF PORTB,CS ; END OF WRITE COMMAND, DESELECT

MOVLW RDCFG
TRIS PORTB ; DIO = INPUT
BSF PORTB,CS ; CS HIGH TO WAIT FOR ACK
WRITE5 
BTFSC PORTB,DIO ; CHECK FOR ACK
GOTO WRITE6 ; WDT RESET ON NO ACK
GOTO WRITE5

WRITE6 BCF PORTB,CS ; END OF ACK

; ******* EEPROM WRITE DISABLE ****************
MOVLW 000H ; WRITE DISABLE COMMAND
MOVWF OUTBYT
CALL SENDC
BCF PORTB,CS ; END OF DISABLE COMMAND, DESELECT

INCF ADDRESS,F ; POINT TO NEXT EEPROM ADDRESS ( BY DEFAULT )
RETLW 0H

;------------------------------------------------------------------------------
;
; FUNCTION : EEREAD () 
;
; DESCRIPTION : READ 16 BIT VALUE FROM EEPROM 
;
; NOTE : THIS ROUTINE MUST BE IN THE LOWER HALF OF THE PAGE
;
;------------------------------------------------------------------------------

EEREAD
MOVFW ADDRESS
MOVWF OUTBYT
BSF OUTBYT,7 ; COMMAND = READ
CALL SENDC ; SEND COMMAND
MOVLW RDCFG
TRIS PORTB ; DIO = INPUT
MOVLW 16D ; 16 BITS TO READ
MOVWF CNT1

READ0 BSF PORTB,CLK ; CLOCK HIGH
RLF TMP2,F ; SHIFT LO BYTE
BCF TMP2,0 ; ASSUME BIT WILL BE 1
BTFSC PORTB,DIO ; READ DIO LINE
BSF TMP2,0 ; COPY BIT TO REGISTER
BCF PORTB,CLK ; CLOCK LOW
RLF TMP1,F ; SHIFT HI BYTE
DECFSZ CNT1,F ; LOOP COUNTER
GOTO READ0
BCF PORTB,CS ; END READ CYCLE

RETLW 0H

;------------------------------------------------------------------------------
;
; FUNCTION : DECRYPT () 
;
; DESCRIPTION : DECRYPTS 32 BIT [HOP1:HOP4] USING [CSR0:CSR7]
;
; NOTE : THIS ROUTINE MUST BE IN THE LOWER HALF OF THE PAGE
;
;------------------------------------------------------------------------------


; THE KEY USED IS A FIXED KEY WHICH IS NOT SERIAL NUMBER DEPENDANT
; THE USER MUST CHOOSE A KEY AND CHANGE THE CODE HERE TO REFLECT THAT KEY

DECRYPT
MOVLW 0EFH ; LOAD FIXED 64 BIT KEY LSB 
MOVWF KEY0
MOVLW 0CDH
MOVWF KEY1
MOVLW 0ABH
MOVWF KEY2
MOVLW 089H
MOVWF KEY3
MOVLW 067H
MOVWF KEY4
MOVLW 045H
MOVWF KEY5
MOVLW 023H
MOVWF KEY6
MOVLW 01H ; LOAD FIXED 64 BIT KEY MSB
MOVWF KEY7

MOVLW 11+1 ; OUTER LOOP 11+1 TIMES 
MOVWF CNT1 ; OUTER LOOP 11+1 TIMES 

DECRYPT_OUTER

MOVLW 48 ; INNER LOOP 48 TIMES
MOVWF CNT0 ; INNER LOOP 48 TIMES

DECRYPT_INNER
CLRWDT ; RESET WATCHDOG TIMER
MOVFW CNT1 ; LAST 48 LOOPS RESTORE THE KEY
XORLW 1 ; LAST 48 LOOPS RESTORE THE KEY
SKPNZ ; LAST 48 LOOPS RESTORE THE KEY
GOTO ROTATE_KEY ; LAST 48 LOOPS RESTORE THE KEY

; THE LOOKUP TABLE IS COMPRESSED INTO IN 4 BYTES TO SAVE SPACE
; USE THE 3 LOW INDEX BITS TO MAKE UP AN 8-BIT BIT MASK
; USE THE 2 HIGH INDEX BITS TO LOOK UP THE VALUE IN THE TABLE
; USE THE BIT MASK TO ISOLATE THE CORRECT BIT IN THE BYTE
; PART OF THE REASON FOR THIS SCHEME IS BECAUSE NORMAL TABLE LOOKUP
; REQUIRES AN ADDITIONAL STACK LEVEL

CLRC ; CLEAR CARRY (FOR THE LEFT SHIFT)

MOVLW 1 ; INITIALISE MASK = 1
BTFSC HOP3,3 ; SHIFT MASK 4X IF BIT 2 SET
MOVLW 10000B ; SHIFT MASK 4X IF BIT 2 SET
MOVWF MASK ; INITIALISE MASK = 1

BTFSS HOP2,0 ; SHIFT MASK ANOTHER 2X IF BIT 1 SET
GOTO $+3
RLF MASK,F
RLF MASK,F 

BTFSC HOP1,0 ; SHIFT MASK ANOTHER 1X IF BIT 0 SET
RLF MASK,F

; MASK HAS NOW BEEN SHIFTED 0-7 TIMES ACCORDING TO BITS 2:1:0

MOVLW 0 ; TABLE INDEX = 0
BTFSC HOP4,1
IORLW 2 ; IF BIT 3 SET ADD 2 TO THE TABLE INDEX
BTFSC HOP4,6
IORLW 4 ; IF BIT 4 SET ADD 4 TO THE TABLE INDEX

ADDWF PC,F ; ADD THE INDEX TO THE PROGRAM COUNTER
; [ MUST BE IN LOWER HALF OF PAGE ]

TABLE
MOVLW 02EH ; BITS 4:3 WERE 00
GOTO TABLE_END ; END OF LOOKUP

MOVLW 074H ; BITS 4:3 WERE 01
GOTO TABLE_END ; END OF LOOKUP

MOVLW 05CH ; BITS 4:3 WERE 10
GOTO TABLE_END ; END OF LOOKUP

MOVLW 03AH ; BITS 4:3 WERE 11

TABLE_END

ANDWF MASK,F ; ISOLATE THE CORRECT BIT BY ANDING WITH MASK
MOVLW 0 ; COPY THE BIT TO BIT 7
SKPZ ; COPY THE BIT TO BIT 7
MOVLW 10000000B ; COPY THE BIT TO BIT 7

XORWF HOP2,W ; ONLY INTERESTED IN BIT HOP2,7
XORWF HOP4,W ; ONLY INTERESTED IN BIT HOP4,7
XORWF KEY1,W ; ONLY INTERESTED IN BIT KEYREG1,7

MOVWF MASK ; STORE W TEMPORARILY (WE NEED BIT 7)
RLF MASK,F ; LEFT ROTATE MASK TO GET BIT 7 INTO THE CARRY

RLF HOP1,F ; SHIFT IN THE NEW BIT
RLF HOP2,F
RLF HOP3,F
RLF HOP4,F

ROTATE_KEY

CLRC ; CLEAR CARRY
BTFSC KEY7,7 ; SET CARRY IF LEFTMOST BIT SET
SETC ; SET CARRY IF LEFTMOST BIT SET

RLF KEY0,F ; LEFT-ROTATE THE 64-BIT KEY 
RLF KEY1,F
RLF KEY2,F
RLF KEY3,F
RLF KEY4,F