Difference between revisions of "83:Ports:04"

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Revision as of 06:24, 30 March 2005

Synopsis

Port Number: 04h

Function: Timer Interrupt Frequency

This port controls the frequency of the hardware timer.

Read Values

  • Bits 0-7: Undocumented. This port is never read by the TIOS.

Write Values

  • Bit 0: Unknown. The calculator crashes when set. Maybe it has more or less the same behaviour as bit 0 of 83Plus:Ports:04.
  • Bits 1 and 2 control the hardware timer frequency. Setting both 0 sets the timer to the fastest speed, and both 1 is the slowest speed. The normal speed is with both bits 1.
  • Bit 3: Unused? Always 0.
  • Bit 4: Unused? Always 1.
  • Bit 5-7: Unknown, but definitely used.