2. 8-bit event counter operation
When bit CH2 is set to 1 in ECCSR, ECH and ECL operate as independent 8-bit event counters.
Figure 9-20 shows an example of the software processing when ECH and ECL are used as 8-bit
event counters.
Start
Set CH2 to 1
Clear CUEH, CUEL, CRCH, and CRCL to 0
Clear OVH to 0
Set CUEH, CUEL, CRCH, and CRCL to 1
End
Figure 9-20 Example of Software Processing when Using ECH and ECL as 8-Bit Event
Counters
ECH and ECL can be used as 8-bit event counters by carrying out the software processing shown
in the example in figure 9-20. The 8-bit event counter operating clock source is asynchronous
event input from the AEVH pin for ECH, and asynchronous event input from the AEVL pin for
ECL. When the next clock is input after the ECH count value reaches H'FF, ECH overflows, the
OVH flag is set to 1 in ECCSR, the ECH count value returns to H'00, and counting up is restarted.
Similarly, when the next clock is input after the ECL count value reaches H'FF, ECL overflows,
the OVL flag is set to 1 in ECCSR, the ECL count value returns to H'00, and counting up is
restarted. When overflow occurs, the IRREC bit is set to 1 in IRR2. If the IENEC bit in IENR2 is
1 at this time, an interrupt request is sent to the CPU.
248
ETC [ ETC ]
