Z88 Developers' Notes
Contents   Contents of System Calls

OS_Alm, alarm manipulation

RST 20H, DEFB $81

IN: 

     A =
          AH_SUSP ($01), suspend alarm
          AH_REV ($02), revive alarms
          AH_RES ($03), reset alarm enable state
          AH_SINC ($04), display symbol
          AH_SDEC ($05), remove symbol (subject to use count)
          AH_SRES ($06), reset symbol

          AH_SET ($07), Set a new alarm:
               BDE = routine address to be called on expiry:
                    B=0, DE   call OS_Alm with (A = AH_CNC ???) IX=handle
                    B<>0, DE  call BDE
               HL = 6 byte date, time.

          AH_CNC ($08), Cancel an alarm:
               IX = alarm handle

          AH_DG1 ($09), Ding-dong type 1
          AH_DG2 ($0A), Ding-dong type 2
          AH_AINC ($0B), action count increment
          AH_ADEC ($0C), action count decrement
          AH_ARES ($0D), action count reset
OUT, always; AH_SUSP, AH_REV, AH_RES, AH_SINC, AH_SDEC, AH_SRES, AH_DG1, AH_DG2, AH_AINC, AH_ADEC, AH_ARES: 
     Fc = 0

     Registers changed after return:
          A.BCDEHL/IXIY same
          .F....../.... different
OUT, AH_SET, if call succeeded: 
     Fc = 0
     IX = alarm handle
OUT, AH_SET, if call failed: 
     Fc = 1
     A = error code.
OUT, AH_CNC, if call succeeded: 
     Fc = 0
     IX = 0
OUT, AH_CNC, if call failed: 
     Fc = 1
     A = error code.

     Registers changed after return, AH_SET, AH_CNC:
          A.BCDEHL/..IY same
          .F....../IX.. different
Notes:
Internal operating system usage.
Bugs:
 

Related calls:

GN_Aab, allocate alarm block
GN_Alp, process an expired alarm (internal OZ usage)
GN_Fab, free alarm block
GN_Lab, link an alarm block into the alarm chain
GN_Uab, unlink an alarm block from the alarm chain