Function 90h    Device Busy Loop                         (except PC, PCjr, XT) 
entry   AH      90h 
	AL      type code: 
		00h     disk 
		01h     diskette 
		02h     keyboard 
		03h     PS/2 pointing device 
		80h     network (ES:BX = pointer to network control block) 
		0FCh    hard disk reset (PS/2) 
		0FDh    diskette motor start 
		0FEh    printer 
	ES:BX   pointer to request block for type codes 80h through 0BFh 
return  CF      1 (set) if wait time satisfied 
		0 (clear) if driver must perform wait 
note    Used by NETBIOS 
	Type codes are allocated as follows: 
	00h-7Fh non-reentrant devices; OS must arbitrate access 
	80h-BFh reentrant devices; ES:BX points to a unique control block 
	C0h-FFh wait-only calls, no complementary int 15, fn91h call 
 
 

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