HD64F3039F18 Datasheet, PDF (349/710 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8 Family / H8/300H Series

Section 10 Watchdog Timer
Writing to RSTCSR
RSTCSR must be written by a word transfer instruction. It cannot be written by byte transfer
instructions. Figure 10.3 shows the format of data written to RSTCSR. To write 0 in the WRST
bit, the write data must have H'A5 in the upper byte and H'00 in the lower byte. The H'00 in the
lower byte clears the WRST bit in RSTCSR to 0. To write to the RSTOE bit, the upper byte must
contain H'5A and the lower byte must contain the write data. Writing this word transfers a write
data value into the RSTOE bit.
Writing 0 in WRST bit
15
87
0
Address H'FFAA*
H'A5
H'00
Writing to RSTOE bit
15
Address H'FFAA*
H'5A
87
0
Write data
Note: * Lower 16 bits of the address.
Figure 10.3 Format of Data Written to RSTCSR
Reading TCNT, TCSR, and RSTCSR
These registers are read like other registers. Byte access instructions can be used. The read
addresses are H'FFA8 for TCSR, H'FFA9 for TCNT, and H'FFAB for RSTCSR, as listed in table
10.3.
Table 10.3 Read Addresses of TCNT, TCSR, and RSTCSR
Address*
Register
H'FFA8
TCSR
H'FFA9
TCNT
H'FFAB
RSTCSR
Note: * Lower 16 bits of the address.
Rev.3.00 Mar. 26, 2007 Page 325 of 682
REJ09B0353-0300