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12.5
Precautions when Using DTP/External Interrupt
This section explains the precautions when using the DTP/external interrupt.
I Precautions when Using DTP/External Interrupt Circuit
G
Condition of external-connected peripheral device when DTP function is used
• When using the DTP function, the peripheral device must automatically clear a data transfer request
when data transfer is performed.
• Inactivate the transfer request signal within three machine clocks after starting data transfer.If the
transfer request signal remains active, the DTP/external interrupt regards the transfer request signal as a
generation of next transfer request.
G
External interrupt input polarity
• When the edge detection is set in the detection level setting register, the pulse width for edge detection
must be at least three machine clocks.
• When a level causing an interrupt factor is input with level detection set in the detection level setting
register, the DTP/external interrupt request flag bit (EIRR: ER) in the DTP/external interrupt factor
register is set to 1 and the factor is held as shown in Figure 12.5-1.
With the factor held in the DTP/external interrupt request flag bit (EIRR: ER), the request to the interrupt
controller remains active if the interrupt request is enabled (ENIR: EN = 1) even after the DTP/external
interrupt factor is cancelled.To cancel the request to the interrupt controller, clear the DTP/external
interrupt request flag bit (EIRR: ER) as shown in Figure 12.5-2.
DTP/external
interrupt factor
Figure 12.5-1 Clearing Factor Hold Circuit when Level Set
DTP/interrupt input
detection circuit
Hold the factor untill clearing
DTP/external
Enable gate
interrupt request
flag bit (EIRR: ER)
CHAPTER 12 DTP/external interrupt
To interrupt
controller
(interrupt request)
343
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