HD64F3039F18 Datasheet, PDF (348/710 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8 Family / H8/300H Series

Section 10 Watchdog Timer
10.2.4 Notes on Register Access
The watchdog timer's TCNT, TCSR, and RSTCSR registers differ from other registers in being
more difficult to write. The procedures for writing and reading these registers are given below.
Writing to TCNT and TCSR
These registers must be written by a word transfer instruction. They cannot be written by byte
instructions. Figure 10.2 shows the format of data written to TCNT and TCSR. TCNT and TCSR
both have the same write address. The write data must be contained in the lower byte of the
written word. The upper byte must contain H'5A (password for TCNT) or H'A5 (password for
TCSR). This transfers the write data from the lower byte to TCNT or TCSR.
TCNT write
Address
15
H'FFA8*
H'5A
87
0
Write data
TCSR write
Address
15
H'FFA8*
H'A5
87
0
Write data
Note: * Lower 16 bits of the address.
Figure 10.2 Format of Data Written to TCNT and TCSR
Rev.3.00 Mar. 26, 2007 Page 324 of 682
REJ09B0353-0300