RX610 Group
17. 8-Bit Timer (TMR)
R01UH0032EJ0120 Rev.1.20
Page 585 of 1006
Feb 20, 2013
17.7.7
Switching of Internal Clocks and TCNT Operation
TCNT may be incremented erroneously depending on when the internal clock is switched. Table 17.8 shows the
relationship between the timing at which the internal clock is switched (by writing to the TCCR.CKS[2:0] bits) and the
operation of TCNT.
When TCNT clock is generated from an internal clock, the rising edge of the internal clock pulse are always monitored.
If the signal levels of the clocks before and after switching change from low to high as shown in No. 2 in table 17.8, the
change is considered as an edge. Therefore, a TCNT clock pulse is generated and TCNT is incremented.
The erroneous increment of TCNT can also happen when switching between internal and external clocks.
Table 17.8 Switching of Internal Clocks and TCNT Operation
Timing to Change the
TCCR.CKS[2:0] Bits
TCNT Clock Operation
Switching from low to low
*
1
Clock before
switching
Clock after
switching
TCNT
input clock
TCNT
TCCR.CKS[2:0] bits changed
N+1
N
N+2
Switching from low to high
*
2
Clock before
switching
Clock after
switching
TCNT
input clock
TCNT
TCCR.CKS[2:0] bits changed
*
3
N+1
N
N+2
N+3
Summary of Contents for RX600 Series
Page 1006: ...RX610 Group R01UH0032EJ0120 ...
