mc68hc912dg128 Freescale Semiconductor, Inc, mc68hc912dg128 Datasheet - Page 292

• Manufacturer Part Number: mc68hc912dg128
• Description: M68hc12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Inter-IC Bus
15.7.4 Generation of STOP
Technical Data
292
ISR
TRANSMIT
The following is an example of a software response by a ’master
transmitter’ in the interrupt routine (see
A data transfer ends with a STOP signal generated by the ’master’
device. A master transmitter can simply generate a STOP signal after all
the data has been transmitted. The following is an example showing how
a stop condition is generated by a master transmitter.
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 STOP signal is generated by a master receiver.
MASTX
END
EMASTX
MASR
LAMAR
ENMASR
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BCLR
BRCLR
BRCLR
BRSET
MOVB
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DEC
BEQ
MOVB
DEC
BNE
BSET
BRA
BCLR
TST
BEQ
BRSET
MOVB
DEC
BRA
BCLR
RTI
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IBSR,#$02
IBCR,#$20,SLAVE
IBCR,#$10,RECEIVE
IBSR,#$01,END
DATABUF,IBDR
Inter-IC Bus
RXCNT
ENMASR
RXCNT,D1
D1
NXMAR
IBCR,#$08
NXMAR
IBCR,#$20
TXCNT
END
IBSR,#$01,END
DATABUF,IBDR
TXCNT
EMASTX
IBCR,#$20
;DECREASE THE RXCNT
;LAST BYTE TO BE READ
;CHECK SECOND LAST BYTE
;TO BE READ
;NOT LAST OR SECOND LAST
;SECOND LAST, DISABLE ACK
;TRANSMITTING
;LAST ONE, GENERATE ‘STOP’ SIGNAL
;CLEAR THE IBIF FLAG
;BRANCH IF IN SLAVE MODE
;BRANCH IF IN RECEIVE MODE
;IF NO ACK, END OF TRANSMISSION
;TRANSMIT NEXT BYTE OF DATA
;GET VALUE FROM THE
;TRANSMITING COUNTER
;END IF NO MORE DATA
;END IF NO ACK
;TRANSMIT NEXT BYTE OF DATA
;DECREASE THE TXCNT
;EXIT
;GENERATE A STOP CONDITION
;RETURN FROM INTERRUPT
Figure
MC68HC912DG128 — Rev 3.0
15-4).
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