HD6435348R Hitachi Semiconductor, HD6435348R Datasheet - Page 267

• Manufacturer Part Number: HD6435348R
• Description: Single-Chip Microcomputer
• Manufacturer: Hitachi Semiconductor

13.4 Application Notes
Contention between TCNT Write and Increment: If a timer counter clock pulse is generated
during the T
timer counter is not incremented. See figure 13-8.
Changing the Clock Select Bits (CKS2 to CKS0): Software should stop the watchdog timer (by
clearing the TME bit to 0) before changing the value of the clock select bits. If the clock select
bits are modified while the watchdog timer is running, the timer count may be incremented
incorrectly.
Use of Reset Output: When the reset signal is output to external devices, special circuitry is
needed for input of the external reset signal.
The reset output is an NMOS open-drain output.
Figure 13-9 shows an example of a reset circuit.
3
state of a write cycle to the timer counter, the write operation takes priority and the
ø
Internal address bus
Internal write signal
TCNT clock pulse
TCNT
Figure 13-8 TCNT Write-Increment Contention
Write cycle: CPU writes to TCNT
T
1
252
N
TCNT address
T
2
T
3
Counter write data
M