Datasheet

Appendix B Internal I/O Registers
Rev.7.00 Feb. 14, 2007 page 1038 of 1108
REJ09B0089-0700
TCSR—Timer Control/Status Register H'FFBC (W), H'FFBC (R) WDT
Notes: 1. The method for writing to TCSR is different from that for general registers to prevent
accidental overwriting. For details, see section 11.2.4, Notes on Register Access.
2. Can only be written with 0 for flag clearing.
0 [Clearing condition]
When 0 is written to OVF after reading OVF = 1
1
Overflow Flag
0 Interval timer mode: Sends the CPU an interval timer interrupt
request (WOVI) when TCNT overflows
Watchdog timer mode: Generates the WDTOVF signal
*1
when
TCNT overflows
*2
1
Timer Mode Select
0
1
TCNT is initialized to H'00 and halted
TCNT counts
Timer Enable
Clock Select
CKS2
CKS1 CKS0 Clock
Overflow period*
(when φ = 20 MHz)
0
1
0
1
0
1
0
1
0
1
0
1
0
1
φ/2
φ/64
φ/128
φ/512
φ/2048
φ/8192
φ/32768
φ/131072
25.6 μs
819.2 μs
1.6 ms
6.6 ms
26.2 ms
104.9 ms
419.4 ms
1.68s
Note: * The overflow period is the time from when TCNT
starts counting up from H'00 until overflow occurs.
[Setting condition]
When TCNT overflows from H'FF to H'00 in interval timer mode
7
OVF
0
R/(W)
*2
6
WT/IT
0
R/W
5
TME
0
R/W
4
⎯
1
⎯
3
⎯
1
⎯
0
CKS0
0
R/W
2
CKS2
0
R/W
1
CKS1
0
R/W
Bit
Initial value
Read/Write
*1
:
:
:
Notes: 1. The WDTOVF pin function cannot be used in the F-ZTAT
versions.
2. For details of the case where TCNT overflows in watchdog
timer mode, see section 11.2.3, Reset Control/Status Register
(RSTCSR).