INT 7C - SK-UPPS Data Link Interface API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. - SYNC REQUEST BUFFER
	AX = 0012h
	DX = protocol ID (see #03849)
Return: AX = completion code (see #03846)
	if AX=0000h: ES:BX -> Mbuf (see #03847)
Note:	If the protocol wants to be informed when an Mbuf becomes available,
	  REQUEST BUFFER (AX=0004h) should be used instead.
SeeAlso: AX=0004h,AX=0005h,AX=0006h,AX=0013h