Operation As External Event Counter - NEC 78K0 User Manual

8.4.2

Operation as external event counter

The external event counter counts the number of external clock pulses to be input to TI5n by 8-bit timer counter 5n
(TM5n).
TM5n is incremented each time the valid edge specified by timer clock selection register 5n (TCL5n) is input.
Either the rising or falling edge can be selected.
When the TM5n count value matches the value of 8-bit timer compare register 5n (CR5n), TM5n is cleared to 0
and an interrupt request signal (INTTM5n) is generated.
Whenever the TM5n value matches the value of CR5n, INTTM5n is generated.
Setting
<1> Set each register.
• Set the port mode register (PM17 or PM33)
• TCL5n: Select TI5n input edge.
TI5n falling edge → TCL5n = 00H
TI5n rising edge → TCL5n = 01H
• CR5n:
Compare value
• TMC5n: Stop the count operation, select the mode in which clear & start occurs on match of TM5n and
CR5n, disable the timer F/F inversion operation, disable timer output.
(TMC5n = 0000××00B × = Don't care)
<2> When TCE5n = 1 is set, the number of pulses input from TI5n is counted.
<3> When the values of TM5n and CR5n match, INTTM5n is generated (TM5n is cleared to 00H).
<4> After these settings, INTTM5n is generated each time the values of TM5n and CR5n match.
Note 8-bit timer/event counter 50: PM17
8-bit timer/event counter 51: PM33
Figure 8-12. External Event Counter Operation Timing (with Rising Edge Specified)
TI5n
Count start
TM5n count value
CR5n
INTTM5n
Remark N = 00H to FFH
n = 0, 1
CHAPTER 8 8-BIT TIMER/EVENT COUNTERS 50 AND 51
00 01 02 03 04
User's Manual U15947EJ2V0UD
Note
to 1.
*
N − 1
05 N 00 01 02 03
N
223