HD6432646 Hitachi, HD6432646 Datasheet - Page 457

• Manufacturer Part Number: HD6432646
• Description: (HD64F264x Series) 16-Bit Microcomputer
• Manufacturer: Hitachi

12.2.4
The watchdog timer’s TCNT, TCSR, and RSTCSR registers differ from other registers in being
more difficult to write to. The procedures for writing to and reading these registers are given
below.
Writing to TCNT and TCSR: These registers must be written to by a word transfer instruction.
They cannot be written to with byte instructions.
Figure 12-2 shows the format of data written to TCNT and TCSR. TCNT and TCSR both have the
same write address. For a write to TCNT, the upper byte of the written word must contain H'5A
and the lower byte must contain the write data. For a write to TCSR, the upper byte of the written
word must contain H'A5 and the lower byte must contain the write data. This transfers the write
data from the lower byte to TCNT or TCSR.
TCNT write
TCSR write
Notes on Register Access
Address: H'FF74
Address: H'FF74
Figure 12-2 Format of Data Written to TCNT and TCSR (WDT0)
15
15
H'5A
H'A5
8 7
8 7
Write data
Write data
0
0
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