83:Ports:04

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.