HD64F2638F20J Datasheet, PDF (488/1512 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

Section 12 Watchdog Timer
H8S/2639, H8S/2638, H8S/2636,
H8S/2630, H8S/2635 Group
Writing to RSTCSR: RSTCSR must be written to by word transfer instruction to address
H'FF76. It cannot be written to with byte instructions.
Figure 12-3 shows the format of data written to RSTCSR. The method of writing 0 to the WOVF
bit differs from that for writing to the RSTE bit.
To write 0 to the WOVF bit, the write data must have H'A5 in the upper byte and H'00 in the
lower byte. This clears the WOVF bit to 0, but has no effect on the RSTE bit. To write to the
RSTE bit, the upper byte must contain H'5A and the lower byte must contain the write data. This
writes the values in bits 6 and 5 of the lower byte into the RSTE bit, but has no effect on the
WOVF bit.
Writing 0 to WOVF bit
15
87
0
Address: H'FF76
H'A5
H'00
Writing to RSTE bit
15
Address: H'FF76
H'5A
87
0
Write data
Figure 12-3 Format of Data Written to RSTCSR (WDT0)
Reading TCNT, TCSR, and RSTCSR (WDT0): These registers are read in the same way as
other registers. The read addresses are H'FF74 for TCSR, H'FF75 for TCNT, and H'FF77 for
RSTCSR.
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REJ09B0103-0800 Rev. 8.00
May 28, 2010