r4f2456 Renesas Electronics Corporation., r4f2456 Datasheet - Page 851

• Manufacturer Part Number: r4f2456
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2400 Series
• Manufacturer: Renesas Electronics Corporation.

14.6
14.6.1
The watchdog timer’s TCNT, TCSR, and RSTCSR registers differ from other registers in being
more difficult to write to. The procedures for writing to and reading these registers are given
below.
(1)
TCNT and TCSR must be written to by a word transfer instruction. They cannot be written to by a
byte transfer instruction.
TCNT and TCSR both have the same write address. Therefore, satisfy the relative condition
shown in figure 14.4 to write to TCNT or TCSR. The transfer instruction writes the lower byte
data to TCNT or TCSR according to the satisfied condition.
To write to RSTCSR, execute a word transfer instruction for address H'FFBE. A byte transfer
instruction cannot perform writing to RSTCSR.
The method of writing 0 to the WOVF bit differs from that of writing to the RSTE bit. To write 0
to the WOVF bit, satisfy the lower condition shown in figure 14.4.
If satisfied, the transfer instruction clears the WOVF bit to 0, but has no effect on the RSTE bit.
To write to the RSTE bit, satisfy the above condition shown in figure 14.4. If satisfied, the transfer
instruction writes the value in bit 6 of the lower byte into the RSTE bit, but has no effect on the
WOVF bit.
Writing to TCNT, TCSR, and RSTCSR
Usage Notes
Notes on Register Access
Rev. 1.00 Sep. 19, 2008 Page 821 of 1342
Section 14 Watchdog Timer (WDT)
REJ09B0467-0100