Renesas H8S/2158, User Manual

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Section 7 Data Transfer Controller (DTC)
Rev. 3.00 Jan 25, 2006 page 152 of 872
REJ09B0286-0300
7.3 Activation Sources
The DTC is activated by an interrupt request or by a write to DTVECR by software. The interrupt
request source to activate the DTC is selected by DTCER. At the end of a data transfer (or the last
consecutive transfer in the case of chain transfer), the interrupt flag that became the activation
source or the corresponding DTCER bit is cleared. The activation source flag, in the case of RXI0,
for example, is the RDRF flag in SCI_0.
When an interrupt has been designated as a DTC activation source, the 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 7.2 shows a block
diagram of DTC activation source control. For details on the interrupt controller, see section 5,
Interrupt Controller.
CPU
DTC
DTCER
Source flag cleared
On-chip
peripheral
module
IRQ interrupt
Interrupt
request
Clear
Clear
controller
Clear request
Interrupt controller
Selection circuit
Interrupt mask
Select
DTVECR
Figure 7.2 Block Diagram of DTC Activation Source Control