HD6437020 Datasheet, PDF (347/507 Pages) Hitachi Semiconductor – SuperH™ RISC engine

12.2.4 Register Access
The watchdog timer’s TCNT, TCSR, and RSTCSR registers differ from other registers in that they
are more difficult to write. The procedures for writing and reading these registers are given below.
Writing to the TCNT and TCSR: These registers must be written by a word transfer instruction.
They cannot be written by byte transfer instructions. The 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 be H'5A (for the TCNT) or H'A5 (for the TCSR) (figure 12.2). This transfers the write
data from the lower byte to the TCNT or TCSR.
Writing to the TCNT
Address:
H'5FFFFB8
15
8
H'5A
7
0
Write data
Writing to the TCSR
Address:
H'5FFFFB8
15
8
H'A5
7
0
Write data
Figure 12.2 Writing to the TCNT and TCSR
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