) Call European MS-DOS 4.0 device helper function with: DL = function 00h "SchedClock" called on each timer tick AL = tick interval in milliseconds 01h "DevDone" device I/O complete ES:BX -> request header Note: must update status word first; may be called from an interrupt handler 02h "PullRequest" pull next request from queue DS:SI -> DWORD pointer to start of device's request queue Return: ZF clear if pending request ES:BX -> request header ZF set if no more requests 03h "PullParticular" remove specific request from queue DS:SI -> DWORD pointer to start of device's request queue ES:BX -> request header Return: ZF set if request header not found 04h "PushRequest" push the request onto the queue DS:SI -> DWORD pointer to start of device's request queue ES:BX -> request header interrupts disabled 05h "ConsInputFilter" keyboard input check AX = character (high byte 00h if PC ASCII character) Return: ZF set if character should be discarded ZF clear if character should be handled normally Note: called by keyboard interrupt handler so DOS can scan for special input characters 06h "SortRequest" push request in sorted order by starting sector DS:SI -> DWORD pointer to start of device's request queue ES:BX -> request header interrupts disabled 07h "SigEvent" send signal on keyboard event AH = event identifier Return: AL,FLAGS destroyed 09h "ProcBlock" block on event AX:BX = event identifier (typically a pointer) CX = timeout in ms or 0000h for never DH = interruptable flag (nonzero if pause may be interrupted) interrupts disabled Return: after corresponding ProcRun call CF clear if event wakeup, set if unusual wakeup ZF set if timeout wakeup, clear if interrupted AL = wakeup code, nonzero if unusual wakeup interrupts enabled BX,CX,DX destroyed Note: block process and schedules another to run 0Ah "ProcRun" unblock process AX:BX = event identifier (typically a pointer) Return: AX = number of processes awakened ZF set if no processes awakened BX,CX,DX destroyed 0Bh "QueueInit" initialize/clear character queue DS:BX -> character queue structure (see #02600) Note: the queue size field must be set before calling 0Dh "QueueWrite" put a character in the queue DS:BX -> character queue (see #02600) AL = character to append to end of queue Return: ZF set if queue is full ZF clear if character stored 0Eh "QueueRead" get a character from the queue DS:BX -> character queue (see #02600) Return: ZF set if queue is empty ZF clear if characters in queue AL = first character in queue 10h "GetDOSVar" return pointer to DOS variable AL = index of variable 03h current process ID BX = index into variable if AL specifies an array CX = expected length of variable Return: CF clear if successful DX:AX -> variable CF set on error AX,DX destroyed BX,CX destroyed Note: the variables may not be modified 14h "Yield" yield CPU if higher-priority task ready to run Return: FLAGS destroyed 1Bh "CritEnter" begin system critical section DS:BX -> semaphore (6 BYTEs, initialized to zero) Return: AX,BX,CX,DX destroyed 1Ch "CritLeave" end system critical section DS:BX -> semaphore (6 BYTEs, initialized to zero) Return: AX,BX,CX,DX destroyed Note: must be called in the context of the process which called CritEnter on the semaphore Note: the DWORD pointing at the request queue must be allocated by the driver and initialized to 0000h:0000h. It always points at the next request to be executed