Interrupts; Sample Application - Hitachi H8/329 Series Hardware Manual

7.4 Interrupts

Each channel in the 8-bit timer can generate three types of interrupts: compare-match A and B
(CMIA and CMIB), and overflow (OVI). Each interrupt is requested when the corresponding
enable bits are set in the TCR and TCSR. Independent signals are sent to the interrupt controller
for each interrupt. Table 7-3 lists information about these interrupts.
Table 7-3. 8-Bit Timer Interrupts
Interrupt Description
CMIA Requested when CMFA and CMIEA are set
CMIB Requested when CMFB and CMIEB are set
OVI Requested when OVF and OVIE are set

7.5 Sample Application

In the example below, the 8-bit timer is used to generate a pulse output with a selected duty cycle.
The control bits are set as follows:
(1) In the TCR, CCLR1 is cleared to "0" and CCLR0 is set to "1" so that the timer counter is
cleared when its value matches the constant in TCORA.
(2) In the TCSR, bits OS3 to OS0 are set to "0110," causing the output to change to "1" on
compare-match A and to "0" on compare-match B.
With these settings, the 8-bit timer provides output of pulses at a rate determined by TCORA with a
pulse width determined by TCORB. No software intervention is required.
H'FF
TCORA
TCORB
H'00
TMO pin
TCNT
Figure 7-10. Example of Pulse Output
157
Priority
High
Low
Clear counter