Renesas H8S/2111B Bedienungsanleitung PDF herunterladen (Seite 265)

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Rev. 1.00, 05/04, page 231 of 544

11.6 Usage Notes

11.6.1 Notes on Register Access

The watchdog timer's registers, TCNT and TCSR differ from other registers in being more

difficult to write to. The procedures for writing to and reading from these registers are given

below.

Writing to TCNT and TCSR (Example of WDT_0): These registers must be written to by a

word transfer instruction. They cannot be written to by a byte transfer instruction.

TCNT and TCSR both have the same write address. Therefore, satisfy the relative condition

shown in figure 11.6 to write to TCNT or TCSR. To write to TCNT, the upper bytes must contain

the value H'5A and the lower bytes must contain the write data before the transfer instruction

execution. To write to TCSR, the upper bytes must contain the value H'A5 and the lower bytes

must contain the write data.

Address : H'FFA8

H'5A Write data

15 8 7 0

H'A5 Write data

15 8 7 0

Figure 11.6 Writing to TCNT and TCSR (WDT_0)

Reading from TCNT and TCSR (Example of WDT_0): These registers are read in the same

way as other registers. The read address is H'FFA8 for TCSR and H'FFA9 for TCNT.

1 2 ... 260 261 262 263 264 265 266 267 268 269 270 ... 581 582

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