NAME LinMAC

;###########################################################################
;# LinMac																						#
;# Medium Access Control Layer of the Lin bus										#
;# Written for the LPC932 using the fractional baudrategenerator and	   #
;# the break detection. 																	#
;#																									#
;# Used Recources:																			#
;# -10Byte Data 																			#
;# -Registerbank 3																			#
;# -Bit addressable RAM Byte 21H, 22H, 23H											#
;# -UART with fractional Baudrategenerator											#
;# -Timer0																						#
;# -optional Timer1 or external Interrupt1											#
;#																									#
;# Dipl.-Ing. Lutz Pape 																	#
;# Applications 																			#
;# Microcontroller Business Line															#
;# Philips Semiconductors Hamburg														#
;# 04/05/2002																					#
;#																									#
;# Revision History:																			#
;# Current Version: 1.90																	#
;# V1.0 	: Version for the LPC1 as presented on the Embedded Systems 2002  #
;# V1.90 : implementing new structure with protocol layers						#
;###########################################################################


$INCLUDE (Register.inc) ; CPU Special Function Registers
$INCLUDE (LinMAC.inc)	; Modul includefile
$INCLUDE (LinMAC.cfg)	; Modul configuration

;############################################################################
;## Declarations and Definitions					    #
;############################################################################


;SEGMENT DEFINITIONS
sLinData			SEGMENT DATA  ; various Variables for the protocol
sLinMac 		SEGMENT CODE  ; the code (ISRs and Initroutine)

EXTERN CODE LinMacEvent ; call-back function

; Initialisation routine
PUBLIC InitLinMac 
; public data Bytes
PUBLIC LinFrameLength, LinID, LinData, LinError, LinState
; public State-Flags
PUBLIC LinBreak, LinSynced, LinIDreceived, LinRxData, LinTxData, LinDataRdy, LinFrameRdy, LinSleeps
;public Error-Flags
PUBLIC LinParityError, LinValidationError, LinChecksumError, LinWakeEvent


;Datasegment declaration
RSEG sLinData
;public bytes
LinFrameLength: 		DS 1
LinID:					DS 1
LinData:					DS 8

DSEG AT 18H ; the local Bytes for ISR are stored in Registerbank 3
;local bytes
_miscReg0:				DS 1  ; R0
_miscReg1:				DS 1  ; R1
_miscReg2:				DS 1  ; R2
_LinLastSent:			DS 1  ; R3
_SyncEdgeCount: 	DS 1  ; R4
_LastByteSent:			DS 1  ; R5
_ByteLeft:				DS 1  ; R6
_LinCRC:					DS 1  ; R7

DSEG AT 21H
LinState: DS 1
LinError: DS 1
_Parity:  DS 1

;State Flags
LinBreak				BIT LinState.0	; '1' when Break was detected
LinSynced			BIT LinState.1	; '1' when Syncseq was evaluated
LinIDreceived		BIT LinState.2	; '1' when LinID was received and checked
LinRxData			BIT LinState.3	; '1' when Data is coming in
LinTxData			BIT LinState.4	; '1' when Data is transmitting
LinDataRdy			BIT LinState.5	; '1' when all Data has been received
LinFrameRdy			BIT LinState.6	; '1' when CRC was received and checked
LinSleeps			BIT LinState.7	; '1' when the bus sleeps

;Error Flags
LinParityError			BIT LinError.0 ; '1' when a Parityerror was detected 
LinValidationError   BIT LinError.1 ; '1' when a Validationerror was detected
LinChecksumError		BIT LinError.2 ; '1' when a Checksumerror was detected
LinFrameError			BIT LinError.3 ; '1' when a Frame Error was detected
LinProtocolError     BIT LinError.4 ; '1' when an Error in the Protocolsequence was detected
UARTFramingError		BIT LinError.5 ; '1' when the UART detected a Framing Error
LinWakeEvent		BIT LinError.6 ; '1' when a Wakeup-Event occured in Sleepmode

;ParityFlags
CalcPar0	 BIT _Parity.6
CalcPar1  BIT _Parity.7

;##################################################################################
;#Start of Program								  #
;##################################################################################
;#		Interrupt Vectors																				 #
;##################################################################################

;** UART Rx interrupt **
CSEG AT 23H 
LJMP IntUARTRx

;** UART Tx interrupt **
CSEG AT 6BH
LJMP IntUARTTx

;** Timer1 Interrupt, only when Timer1 is used as Syncseq-Edge-Counter **
$IF (_HW_SYNC_COUNTER) 
CSEG AT 1BH
LJMP IntTimer1
$ENDIF

;** external Int1 Interrupt, only when external Int1 is used as Syncseq-Edge-Counter **
$IF (_SW_SYNC_COUNTER)
CSEG AT 13H
LJMP IntExt1
$ENDIF

;####################################################################################
;#  Program Code																							#
;####################################################################################		
RSEG sLinMac

;#############################################################################
;# UART Rx-routine												   #
;#############################################################################
IntUARTRx:
						PUSH PSW
						PUSH ACC
						CLR ESR
						
						ORL	PSW,#18H;	; use Registerbank 3
			; first test, if the bus is in Sleepmode
						JNB	LinSleeps,_normalActivity
;***********************************************************************************						
; test wakeup-frame
;***********************************************************************************
						MOV	A,SBUF
						JZ		_wakeevent ; '0' received
						CLR	C
						RLC	A
						JNC   _nowakeevent ; MSB was '0'-> can't be a wakeup-character
						ANL   A,#7FH	   ; clear MSB
						JNZ	_nowakeevent ; if, except MSB, any '1' in the char, it can't be the wakeup-char
_wakeevent:	
						SETB	LinWakeEvent
;###############################################################
;# Return from Interrupt functions										#		
;#which can be called to return from the Interrupt routine.    #
;#Course of the LJMPs this is 2-clock cycles slower than the   #
;#'normal' procedure but saves several bytes of code.	       #
;#These functions are only valid for the ISR of UART Rx.       #
;###############################################################
_Errorreturn: ;a return when an Error raised
						MOV LinState,#0
_Eventreturn: ;a return with the LCALL to LinMacEvent
						LCALL LinMacEvent
_nowakeevent:
_RxReti:		  ;a return without LCALL to LinMacEvent		
						ANL SSTAT,#0F1H ; reset the SSTAT register
						POP ACC
						POP PSW
						CLR RI
						SETB ESR
						RETI
						
;*********************************************************************************						
_normalActivity:
;*********************************************************************************
; test on Breakevent
						MOV A,SSTAT
						ANL A,#04H    ; mask Break Bit
						JZ	_noBreak
;********************************************************************************
;Break detected   
;********************************************************************************
						MOV LinState,#1 ; set Breakflag
						SETB P2.0	; ** DEBUG **
						
		;*****************************************************
		;*prepare Timer and counter to evaluate sync sequence*
		;*****************************************************
						CLR TR0 
				$IF (_HW_SYNC_COUNTER)
						MOV TL1,#0FFH			; next falling edge on T1 generates an interrupt
						MOV TH1,#0FFH	
						SETB TR1					; enable counter
						SETB ET1				   ; enable interrupt
						MOV TL0,#0
						MOV TH0,#0 ; clear Timer 0
				$ENDIF
				$IF (_SW_SYNC_COUNTER)
						MOV R4,#5 ;preload number of edges to count (_SyncEdgeCount = R4 in Registerbank 3)
						CLR IE1
						SETB EX1					 ;enable external Interrupt
						MOV TL0,#0FDH;	Offset of -3, because stopping the timer needs three instructioncycles
						MOV TH0,#0FFH
				$ENDIF
												
		;Timer and/or external Int are prepared to evaluate the sync-field	
						SJMP _Eventreturn	
_reti1: 
;********************************************************************************
;no Break --> normal data-reception
;********************************************************************************
_noBreak:	  
						JB  FE,_UARTFramingError
						JNB LinBreak,_ProtocolError  ; Break has to be detected first
						JNB LinSynced,_ProtocolError ; the controller has to be synced first
_testIDBit:
						JB LinIDreceived,_testdatardy
						AJMP _evaluate_ID
_testdatardy:
						JNB LinDataRdy,_process_data
_testframerdy:
						JNB LinFrameRdy,_process_CRC
					;when the controller reaches this point,
					;it expected less data bytes than sent, and
					;accidentally the last data-byte was equal to
					;the CRC, so that no CRC-Error raised.
					;I now set the Framing-Error.
						SETB LinFrameError  ;Frame Error
						SJMP _Errorreturn	

_UARTFramingError:
						SETB UARTFramingError
						CLR FE
						SJMP _Errorreturn				
						
_ProtocolError:
						SETB LinProtocolError
						SJMP _Errorreturn

;********************************************************************************
;CRC reception and test
;********************************************************************************
_process_CRC:						
						MOV A,SBUF								;  CRC in Accumulator
						JNB LinTxData,_checkCRC 	;test if the CRC was transmittet by this node itself (Flag LinTxData)
						CJNE A,_LinLastSent,__validationError ;validation
			
						SJMP _checkCRC
__validationError:
						SETB LinValidationError
						SJMP _Errorreturn
;*************************************************		

_checkCRC:
						ADD A,R7 ; _LinCRC
						CJNE A,#0FFH,_CRCError ; sum must be 0xFF
;Lin Frame Ok
						MOV LinState,#01100111B; set Lin status bits; reset LinTxData, LinRxdata, set Frameready, Datardy, Id, Break and Sync
						AJMP _EventReturn
;*********************************************************
				
_CRCError:			SETB LinChecksumError
						AJMP _Errorreturn
						
;********************************************************************************
;Process the data reception
;********************************************************************************
_process_data:
						JB LinTxData,_do_not_set_bit
						SETB LinRxData
_do_not_set_bit:				
						MOV A,#LinData
						ADD A,R6;_ByteLeft
						MOV R1,A
						MOV @R1,SBUF ;receive the data
;calculate CRC
_calcCRC:	
						MOV A,R7;_LinCRC
						ADDC A,@R1
						JNC _noadd
						INC A
_noadd:
						MOV R7,A ;save CRC	; _LinCRC		
;test if this was the last byte
						MOV A,R6;_ByteLeft
						JNZ _next_is_data
			SETB LinDataRdy
_next_is_data:
						DEC R6;_ByteLeft
						JNB LinTxData,__RxReti; again, test if this node has to transmit the Lin-data
						;validate the last data
						MOV A,@R1
						CJNE A,_LinLastSent,__validationError;
						JB LinDataRdy,_sendCRC
;send the next databyte
						MOV A,#LinData
						ADD A,R6;_ByteLeft
						MOV R1,A
						MOV SBUF,@R1
						MOV _LinLastSent,@R1;
						AJMP _RxReti