Renesas H8S/2633 Series Hardware Manual page 737

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 15-3 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 and RSTS bits.
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 and RSTS bits. To write
to the RSTE and RSTS bits, 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 and RSTS bits,
but has no effect on the WOVF bit.
Writing 0 to WOVF bit
Address: H'FF76
Writing to RSTE and RSTS bits
Address: H'FF76
Figure 15-3 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.
15
H'A5
15
H'5A
8 7
H'00
8 7
Write data
0
0
683