245
Start
End
Set CH2 to 1
Clear CUEH, CUEL, CRCH, and CRCL to 0
Clear OVH, OVL to 0
Set CUEH, CUEL, CRCH, and CRCL to 1
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.
9.7.4
Asynchronous Event Counter Operation Modes
Asynchronous event counter operation modes are shown in table 9.21.
Table 9.21
Asynchronous Event Counter Operation Modes
Operation Mode
Reset Active
Sleep
Watch
Sub-
active
Sub-
sleep
Standby
Module
Standby
ECCSR
Reset
Functions Functions
Held
*
Functions Functions Held
*
Held
ECH
Reset
Functions Functions
*
Functions
*
Functions Functions Functions
*
Halted
ECL
Reset
Functions Functions
*
Functions
*
Functions Functions Functions
*
Halted
Note:
*
When an asynchronous external event is input, the counter increments but the counter
overflow H/L flags are not affected.