AN1212 Freescale Semiconductor / Motorola, AN1212 Datasheet - Page 26

• Manufacturer Part Number: AN1212
• Description: J1850 Multiplex Bus Communication Using the MC68HC705C8 and the SC371016 J1850 Communications Interface (JCI)
• Manufacturer: Freescale Semiconductor / Motorola

AN1212/D
Error Handling
26
NO
NO
INTO INTO NEXT Rx BUFFER
INTO SPDR, INITIATING
LOCATION "data" INTO
LOCATION "command"
LOAD BYTE IN SPDR
MEMORY LOCATION
LOAD BYTE IN RAM
LOAD BYTE IN RAM
LOAD BYTE IN RAM
LOCATION "status"
SPDR, INITIATING
LOCATION "data"
INTO MCU RAM
SPI TRANSFER
SPI TRANSFER
SPI TRANSFER
SPI TRANSFER
COMPLETE?
COMPLETE?
YES
YES
IS
IS
C
B
Figure 14. IRQ Interrupt Service Routine (Sheet 2 of 2)
J1850 Multiplex Bus Communication Using the MC68HC705C8
and the SC371016 J1850 Communications Interface (JCI)
These basic driver routines do not contain extensive error handling procedures.
For received messages, the basic assumption made is "if it is no good, don’t
bother the host with it". Any messages being received which contain errors are
simply discarded. Likewise, when transmission or bus errors are detected there
are no procedures for dealing with them, since in many instances there is not
much the node can do to prevent them from occurring.
However, the JCI can supply the host MCU with extensive transmit, receive,
and bus error information, which the host can use to perform any procedures
deemed necessary whenever any of these errors are detected on the MUX bus.
Freescale Semiconductor, Inc.
For More Information On This Product,
NO
Go to: www.freescale.com
RAM LOCATION "command"
COMBINATION INTO MCU
LOAD "flush message" BIT
INTO SPDR, INITIATING
LOAD BYTE IN SPDR
LOAD BYTE IN RAM
LOCATION "status"
LOCATION "data"
INTO MCU RAM
SPI TRANSFER
SPI TRANSFER
COMPLETE?
YES
IS
A
NO
INTO SPDR, INITIATING
LOCATION "command"
RESTORE "command"
FROM TEMPORARY
LOAD BYTE IN RAM
AND "data" VALUES
SPI TRANSFER
SPI TRANSFER
RETURN FROM
COMPLETE?
INTERRUPT
YES
STORAGE
IS
MOTOROLA