UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 550

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

20.3.5 Watchdog Timer Mode Register (WDM)
non-maskable interrupts.
code configuration (4 bytes), and a write is not performed unless the 3rd and 4th bytes of the operation code are mutual
1’s complements.
interrupt is generated. In this case, the return address saved in the stack area is the address of the instruction that was
the source of the error, and thus the address that was the source of the error can be identified from the return address saved
in the stack area.
RA78K4, only the correct dedicated instruction is generated when MOV WDM, #byte is written), system initialization should
be performed by the program.
operation. That is, a write is not performed to the WDM, and an interrupt such as an operand error interrupt is not generated.
510
The PRC bit of the WDM specifies the priority of NMI pin input non-maskable interrupts and watchdog timer overflow
The WDM can be written to only by a dedicated instruction. This dedicated instruction, MOV WDM, #byte, has a special
If the 3rd and 4th bytes of the operation code are not 1’s complements, a write is not performed and an operand error
If recovery from an operand error is simply performed by means of an RETB instruction, an endless loop will result.
As an operand error interrupt is only generated in the event of an inadvertent program loop (with the NEC assembler,
Other write instructions (MOV WDM, A; AND WDM, #byte; SET1 WDM.7, etc.) are ignored and do not perform any
The WDM can be read at any time by a data transfer instruction.
RESET input clears the WDM register to 00H.
Caution The watchdog timer mode register (WDM) can only be written to with a dedicated instruction
WDM
RUN
(MOV WDM, #byte).
7
6
0
Figure 20-5 Watchdog Timer Mode Register (WDM) Format
5
0
PRC
4
CHAPTER 20 INTERRUPT FUNCTIONS
3
0
WDI2
2
WDI1
1
0
0
See Figure 12-2 in CHAPTER 12 WATCHDOG
TIMER FUNCTION for details.
0FFC2H
PRC
Address
0
1
Watchdog Timer Interrupt Request Priority
Specification
Watchdog timer interrupt request <
NMI pin input interrupt request
Watchdog timer interrupt request >
NMI pin input interrupt request
On Reset
00H
R/W
R/W