DF2211NP24V Renesas Technology / Hitachi Semiconductor, DF2211NP24V Datasheet - Page 400

• Manufacturer Part Number: DF2211NP24V
• Description: H8S/2200 Series, 2212 Group, USB, RTC, HSS TNP-64B; Vcc= 2.7 to 3.6 volts, Temp= -20 to 75 C; Package: PVQN0064LB-A
• Manufacturer: Renesas Technology / Hitachi Semiconductor

10.5
10.5.1
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 transfer instructions. Figure 10.6 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.
Writing to RSTCSR: RSTCSR must be written to by a word transfer to address H'FF76. It cannot
be written to with byte instructions. Figure 10.7 shows the format of data written to RSTCSR. The
method of writing 0 to the WOVF bit differs from that for writing to the RSTE and RSTS bits.
To write 0 to the WOVF bit, the upper byte of the written word must contain H'A5 and the lower
byte must contain H'00. This clears the WOVF bit to 0, but has no effect on the RSTE and RSTS
bits. To write to the RSTE and RSTS bits, the upper byte must contain H'5A and the lower byte
must contain the write data. This writes the values in bits 6 and 5 of the lower byte into the RSTE
and RSTS bits, but has no effect on the WOVF bit.
Rev.7.00 Dec. 24, 2008 Page 346 of 698
REJ09B0074-0700
TCNT write
TCSR write
Usage Notes
Notes on Register Access
Figure 10.6 Format of Data Written to TCNT and TCSR
Address: H'FF74
Address: H'FF74
15
15
H'5A
H'A5
8 7
8 7
Write data
Write data
0
0