DS80C390_00 Datasheet, PDF (138/155 Pages) Dallas Semiconductor – High-Speed Microcontroller User’s Guide Supplement

DS80C390 High-Speed Microcontroller User’s Guide Supplement
SFR Register. Software must clear the respective INTRQ bit in the associated CAN 0/1 Message (1-15)
Control Register to clear the interrupt source before leaving the interrupt routine.
The CAN 0/1 Interrupt source is connected to a change in the CAN 0/1 Status Register. Each of the status
bits in the CAN 0/1 Status Register represents a potential source for the interrupt. To simplify the
application and testing of a device, these sources are broken into two groups which are further enabled via
the ERIE and STIE bits of the CAN 0/1 Control register. This allows the non-standard errors typically
associated with development to be grouped under the STIE enable. These include the successful receive
RXS, successful transmit TXS, wake status WKS, and general set of error conditions reported by ER2 -
ER0. Also note that since the RXS and TXS bit are cleared by software, if a second message is received
or transmitted before the RXS or TXS bits are cleared and after a read of the CAN 0/1 Status Register, a
second interrupt will be generated. The remaining error sources comprise the BSS and CECE bits in the
CAN 0/1 Status Register. These read-only bits are separately enabled via the ERIE bit in the CAN 0/1
Control register. A read of the CAN 0/1 Status Register is required to clear either of the two groups of
Error interrupts. It is possible that multiple changes to the Status Register may occur before the register is
read; in that case the Status Register will generate only one interrupt. The following figure provides a
graphical illustration of the interrupt sources and their respective interrupt enables.
Figure 16- 10 CAN Interrupt Logic
CxIE
EA
INTERRUPT
VECTOR
63 HEX
CAN 0/1
CONTROL ERIE STIE
REGISTER
1 _DQ
C
R
CAN 0/1 STATUS
REGISTER READ
CAN 0/1 MESSAGE 1
CONTROL REGISTER ^ETI
ERI INTRQ
SUCCESSFUL RECEIVE
MESSAGE CENTER1
SUCCESSFUL TRANSMIT
MESSAGE CENTER 1
MESSAGE CENTER 1
MESSAGE CENTER 15
138 of 155
UPDATE CAN 0/1
INTERRUPT
REGISTER