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8.3
Activation Sources
The DTC operates when activated by an interrupt or by a write to DTVECR by software. An
interrupt request can be directed to the CPU or DTC, as designated by the corresponding DTCER
bit. At the end of a data transfer (or the last consecutive transfer in the case of chain transfer), the
activation source or corresponding DTCER bit is cleared. The activation source flag, in the case of
RXI0, for example, is the RDRF flag of SCI channel 0.
When an interrupt has been designated a DTC activation source, existing CPU mask level and
interrupt controller priorities have no effect. If there is more than one activation source at the same
time, the DTC operates in accordance with the default priorities. Figure 8.2 shows a block diagram
of activation source control. For details see section 5, Interrupt Controller.
Table 8.1
Activation Source and DTCER Clearance
Activation Source
When the DISEL Bit is 0 and the
Specified Number of Transfer
Have not Ended
When the DISEL Bit is 1, or when
the Specified Number of Transfers
Have Ended
Software activation
The SWDTE bit is cleared to 0
The SWDTE bit remains set to 1
An interrupt is issued to the CPU
Interrupt activation
The corresponding DTCER bit
remains set to 1
The activation source flag is
cleared to 0
The corresponding DTCER bit is
cleared to 0
The activation source flag remains
set to 1
A request is issued to the CPU for
the activation source interrupt
CPU
DTC
DTCER
Source flag cleared
On-chip
supporting
module
IRQ interrupt
Interrupt
request
Clear
Clear
controller
Clear request
Interrupt controller
Selection circuit
Interrupt mask
Select
DTVECR
Figure 8.2 Block Diagram of DTC Activation Source Control
Summary of Contents for H8S/2215 Series
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