Nintendo GAME BOY Programming Manual page 223

When writing values to the clock counters:
•
Set data in clock counter register RTC_S.
•
Set data in clock counter register RTC_M.
•
Set data in clock counter register RTC_H.
•
Set data in clock counter register RTC_DL.
•
Set data in clock counter register RTC_DH.
3.5.2 Condensation
MBC3 uses a crystal oscillator for its clock counter operation, and condensation on the oscillator
may halt its oscillation, preventing the clocks from counting up. Once the condensation disappears,
the clocks will resume counting up from where they stopped. However, please ensure that the
counter stoppage does not result in a loss of program control.
3.5.3 Control Register Initialization
Although control registers 0-3 are initialized (see Section 3.2, Description of Registers) when Game
Boy power is turned on, they are not initialized by a hard reset of SNES when Super Game Boy is
used. Therefore, please be sure to implement a software reset of these registers.
3.5.4 Clock Counter Registers
When commercial Game Boy software that uses MBC3 is shipped from the factory, the values of
the clock counter registers are undefined. Therefore, please ensure that these registers are
initialized.
Chapter 8: Game Boy Memory Controllers (MBC)
4-cycle delay required
4-cycle delay required
4-cycle delay required
4-cycle delay required
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