HD64F2168 Datasheet, PDF (201/874 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer

7.3.2 Usage Notes
There are following usage notes for this event counter because it uses the DTC. If these usage
notes are not permitted in some applications, use functions such as 8-bit timer event count.
1. Continuous events that are input from the same pin and out of DTC handling are ignored
because the count up is operated by means of the DTC.
2. If some events are generated in short intervals, the priority of event counter handling is not
ordered and events are not handled in order of arrival.
3. If the counter overflows, this event counter counts from H'0000 without generating an
interrupt.
7.4 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.
Source flag cleared
Clear
DTCER
Select
Clear
controller
Clear request
On-chip
peripheral
module
DTC
IRQ interrupt _Interrupt
request
DTVECR
Interrupt controller
Interrupt mask
CPU
Figure 7.2 Block Diagram of DTC Activation Source Control
Rev. 3.00, 03/04, page 161 of 830