p2125vps20 Renesas Electronics Corporation., p2125vps20 Datasheet - Page 350

• Manufacturer Part Number: p2125vps20
• Description: 16-bit Single-chip Microcomputer H8s Family / H8s/2100 Series
• Manufacturer: Renesas Electronics Corporation.

Section 14 Watchdog Timer (WDT)
14.6
14.6.1
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.
(1)
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 14.5 to write to TCNT or TCSR. To write to TCNT, the higher 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 higher bytes must contain the value H'A5 and the lower bytes
must contain the write data.
(2)
These registers are read in the same way as other registers. The read address is H'FFA8 for TCSR
and H'FFA9 for TCNT.
Rev. 1.00 Sep. 21, 2006 Page 312 of 658
REJ09B0310-0100
Writing to TCNT and TCSR (Example of WDT_0)
Reading from TCNT and TCSR (Example of WDT_0)
<TCSR write>
<TCNT write>
Usage Notes
Notes on Register Access
Address : H'FFA8
Address : H'FFA8
Figure 14.5 Writing to TCNT and TCSR (WDT_0)
15
15
H'5A
H'A5
8 7
8 7
Write data
Write data
0
0