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Figure 18.5-2 shows the operation of the DTP/external interrupt circuit.
Figure 18.5-2 Operation of the DTP/external Interrupt Circuit
DTP/external interrupt circuit
Another request
ELVR
ELVR
ELVR
Cause
Generation of DTP/
external interrupt request
Accepted by
interrupt controller?
Accepted by CPU?
Start interrupt processing
microprogram
ICR: ISE
0
Start external interrupt flag.
Processing. Clear interrupt flag.
Return from external interrupt
CHAPTER 18 DTP/EXTERNAL INTERRUPT CIRCUIT
Interrupt controller
ICR
YY
CMP
ICR
XX
DTP handling routine
(EI
2
OS is started)
Transfer data between memory
and peripheral
Update descriptor
Descriptor
data counter
≠ 0
Return from DTP handling routine
1
CPU
IL
Interrupt processing
CMP
microprogram
ILM
0
Interrupt processing routine
Set again or stop
Return to CPU processing
527
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