AH = 4Eh: Light Sleep Control In Int 16h, Fcns {01h,11h}

This function enables or disables light sleep in Int 16h, Fcns {01h,11h} key tests. If light sleep is disabled, the display time out (Auto-Timeout) is also disabled. This function should be used with caution since the light sleep disabled state is power consumptive if light sleep (and more importantly, Auto-Timeout) is disabled indefinitely.

• Input: AH = 4Eh
  AL = 00h, light sleep disabled, display time out disabled.
  AL = 01h, light sleep enabled
  AL > 01h - NOP

• Output: Light sleep enabled or disabled depending on value of AL at entry. This function sets bit 0 of 40h:LteSlpFL to NOT(AL).
• Registers modified: None

• If light sleep is disabled, the Int 16h functions 01h and 11h are designed to skip the call to Int 15h, Function 4100h (skip light sleep). Due to a minor bug, the call will still be made if any annunciators (SHF, Fn, or CAPS Lock) are on.
• The Timer0 Service routine checks LteSlpFL[0]. If light sleep is disabled, the Auto-Timeout counter TimOutCnt is reset from TimOutVal.