)
Values for SK-UPPS Event Upcall event code:
 00h	EV_BUFFER_AVAILABLE client may now call REQUEST BUFFER (AX=0004h)
 01h	EV_ISR_START	    start of Interrupt Service Routine
 02h	EV_ISR_END	    end of ISR (see #03850 [bit 1])
 03h	EV_BUFFER_WANTED    DLI temporarily out of Mbufs
 04h	EV_NETWORK_STATUS   DLI 2.8+ network status -- DX=status (see #03855)
 05h	EV_IO_CONTROL	    DLI 2.8+ I/O control -- DX=subfunc (see AX=0016h)
SeeAlso: #03853