H8SLASH3021 datasheet(347/712 Pages) RENESAS

No. de pieza	H8/3021

Descripción Electrónicos	16-Bit Single-Chip Microcomputer

PDF	712 Pages

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Fabricante Electrónico	RENESAS [Renesas Technology Corp]

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10. Watchdog Timer

Rev.2.00 Mar. 22, 2007 Page 323 of 684

REJ09B0352-0200

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.

8 7

H'5A

Write data

Address

H'FFA8 *

8 7

H'A5

Write data

Address

H'FFA8 *

TCNT write

TCSR write

Note: * Lower 16 bits of the address.

Figure 10.2 Format of Data Written to TCNT and TCSR

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