
SCC/ESCC
User Manual
UM010903-0515 Interfacing the SCC/ESCC
43
some action taken by the processor. The external daisy chain may be controlled by the DLC bit in
WR9. This bit, when set, forces IEO Low, disabling all lower priority devices.
Interrupt Flow Chart (for each interrupt source)
Start
Interrupt Pendi
Set (IP=1)
Master
Interrupt Enabl
(MIE=1)?
Is Peripheral
Enable Pin Ac
(IEI=H)?
Ye
Service (IUS=1)
Interrupt
Condition
Exits?
Specific
Interrupt Enabl
(IEx=1)?
Peripheral Request
Interrupt (INT=L)
IEI/IEO Daisy Chai
CPU Initiates Statu
Decode (INTACK=
Has Higher
Priority Periphera
Disabled Unit?
(IEI=L)
Yes
CPU Services High
Priority Peripher
Priority
Service
Complete?
Interrupt Still
Pending (IP=1)
?
Service
Routine Compl
(Option) Check Oth
Internal IP, Bits,
RESET IUS and Ex
N
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