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Call European MS-DOS 4.0 device helper function with

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Data:

00h

"SchedClock" called on each timer tick

Data:

tick interval in milliseconds

01h

"DevDone" device I/O complete

Data:	ES:BX		request header
Note:	Must update status word first; may be called from an interrupt handler.

02h

"PullRequest" pull next request from queue

Data:

DS:SI

DWORD pointer to start of device's request queue

Return:

clear if pending request

ES:BX

request header

set if no more requests

03h

"PullParticular" remove specific request from queue

Data:	DS:SI		DWORD pointer to start of device's request queue
Data:	ES:BX		request header
Return:	ZF	-	set if request header not found

04h

"PushRequest" push the request onto the queue

Data:	DS:SI		DWORD pointer to start of device's request queue
	ES:BX		request header
	interrupts	-	disabled

05h

"ConsInputFilter" keyboard input check

Data:	AX	=	character (high byte 00h if PC ASCII character)
Return:	ZF	-	set if character should be discarded
Return:	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

Data:	DS:SI		DWORD pointer to start of device's request queue
	ES:BX		request header
	interrupts	-	disabled

07h

"SigEvent" send signal on keyboard event

Data:	AH	=	event identifier
Return:	AL	-	destroyed
Return:	FLAGS	-	destroyed

09h

"ProcBlock" block on event

Data:	AX:BX	=	k process and schedules another to run
	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	-	destroyed
	CX	-	destroyed
	DX	-	destroyed
Note:	Block process and schedules another to run.

0Ah

"ProcRun" unblock process

Data:	AX:BX	=	event identifier (typically a pointer)
Return:	AX	=	number of processes awakened
	ZF	-	set if no processes awakened
	BX	-	destroyed
	CX	-	destroyed
	DX	-	destroyed

0Bh

"QueueInit" initialize/clear character queue

Data:	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

Data:	DS:BX		character queue (see #02600)
Data:	AL	=	character to append to end of queue
Return:	ZF	-	set if queue is full
Return:	ZF	-	clear if character stored

0Eh

"QueueRead" get a character from the queue

Data:

DS:BX

character queue (see #02600)

Return:

set if queue is empty

clear if characters in queue

first character in queue

10h

"GetDOSVar" return pointer to DOS variable

Data:

index of variable

03h

current process ID

index into variable if AL specifies an array

expected length of variable

Return:

clear if successful

DX:AX

variable

set on error

AX	-	destroyed
DX	-	destroyed

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

Data:	DS:BX		semaphore (6 BYTEs, initialized to zero)
Return:	AX	-	destroyed
	BX	-	destroyed
	CX	-	destroyed
	DX	-	destroyed

1Ch

"CritLeave" end system critical section

Data:	DS:BX		semaphore (6 BYTEs, initialized to zero)
Return:	AX	-	destroyed
	BX	-	destroyed
	CX	-	destroyed
	DX	-	destroyed
Note:	Must be called in the context of the process which called CritEnter on the semaphore.

Notes:

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.