Datasheet

M-Bus Module
MOTOROLA MCF5206e USER’S MANUAL 13-13
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ISRLEA.LMBSR,-(A7); LOAD EFFECTIVE ADDR.
BCLR.B#1,(A7)+; CLEAR THE MIF FLAG
MOVE.BMBCR,-(A7); PUSH ADDRESS ON STACK,
BTST.B#5,(A7)+; CHECK THE MSTA FLAG
BEQ.SSLAVE; BRANCH IF SLAVE MODE
MOVE.BMBCR,-(A7); PUSH ADDRESS ON STACK,
BTST.B#4,(A7)+; CHECK THE MODE FLAG
BEQ.SRECEIVE; BRANCH IF IN RECEIVE MODE
MOVE.BMBSR,-(A7); PUSH ADDRESS ON STACK,
BTST.B#0,(A7)+; CHECK ACK FROM RECEIVER
BNE.B END; IF NO ACK, END OF TRANSMISSION
TRANSMITMOVE.BDATABUF,-(A7); STACK DATA BYTE
MOVE.B(A7)+, MBDR; TRANSMIT NEXT BYTE OF DATA
13.6.4 Generation of STOP
A data transfer ends with a STOP signal generated by the'‘master’' device. A master
transmitter can generate a STOP signal after all the data has been transmitted. The
following is an example showing how a master transmitter generates a stop condition.
MASTXMOVE.BMBSR, -(A7); IF NO ACK, BRANCH TO END
BTST.B#0,(A7)+
BNE.B END
MOVE.BTXCNT,D0; GET VALUE FROM THE
; TRANSMITTING COUNTER
BEQ.SEND; IF NO MORE DATA, BRANCH TO
; END
MOVE.BDATABUF,-(A7); TRANSMIT NEXT BYTE OF DATA
MOVE.B(A7)+,MBDR
MOVE.BTXCNT,D0; DECREASE THE TXCNT
SUBQ.L#1,D0
MOVE.BD0,TXCNT
BRA.SEMASTX; EXIT
ENDLEA.LMBCR,-(A7); GENERATE A STOP CONDITION
BCLR.B#5,(A7)+
EMASTXRTE; RETURN FROM INTERRUPT
If a master receiver wants to terminate a data transfer, it must inform the slave transmitter
by not acknowledging the last byte of data, which can be done by setting the transmit
acknowledge bit (TXAK) before reading the 2nd last byte of data. Before reading the last
byte of data, a STOP signal must be generated first. The following is an example showing
how a master receiver generates a STOP signal.
MASRMOVE.BRXCNT,D0;DECREASE RXCNT
SUBQ.L#1,D0
MOVE.BD0,RXCNT
BEQ.SENMASR; LAST BYTE TO BE READ
MOVE.BRXCNT,D1; CHECK SECOND LAST BYTE
EXTB>LD1
SUBI.L#1,D1; TO BE READ
BNE.SNXMAR; NOT LAST ONE OR SECOND LAST
LAMARBSET.B#3,MBCR; SECOND LAST, DISABLE ACK
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eescale S
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