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How to resolve when watchdog timer will underflow?

Latest Updated:06/04/2010

Question:

When erasing a flash memory in CPU rewriting mode, the watchdog timer results underflow. How can I resolve this?

Answer:

  • R8C/1x Series, R8C/2x Series
    In EW1 mode, the CPU will be in a hold state when auto-programming and auto-erasing the user ROM area. With the CPU in the hold state, the peripheral modules do not stop, but the program counter stops and instructions cannot be executed.

    Use EW0 mode. Or perform refresh processing using the suspend function (such as a timer interrupt with a period shorter than that of the watchdog timer) in EW1 mode.

  • R8C/3x Series, R8C/Lx Series
    In EW1 mode, the CPU operates when auto-programming and auto-erasing the data flash area. However, the CPU will be in a hold state when auto-programming and auto-erasing the program ROM area. With the CPU in the hold state, the peripheral modules do not stop, but the program counter stops and instructions cannot be executed.

    To auto-program and auto-erase the program ROM area, use EW0 mode. Or perform refresh processing using the suspend function (such as a timer interrupt with a period shorter than that of the watchdog timer) in EW1 mode.
Suitable Products
R8C/18
R8C/19
R8C/1A
R8C/1B
R8C/20
R8C/21
R8C/22
R8C/23
R8C/24
R8C/25
R8C/26
R8C/27
R8C/28
R8C/29
R8C/2A
R8C/2B
R8C/2C
R8C/2D
R8C/2E
R8C/2F
R8C/2G
R8C/2H
R8C/2J
R8C/2K
R8C/2L
R8C/32C
R8C/33C
R8C/35C
R8C/36C
R8C/38C
R8C/3GC
R8C/3JC
R8C/32D
R8C/33D
R8C/35D
R8C/3GD
R8C/33T
R8C/38A
R8C/L35C
R8C/L36C
R8C/L38C
R8C/L3AC