Int 21 Fn C502  - Novell Netware - Synchronization Services - Wait On Sem  [N]

   AX = C502h
   CX:DX = semaphore handle
   BP = timeout limit in timer ticks (1/18 sec)
       0000h return immediately if semaphore already zero or negative

Return: AL = status
       00h successful
       FEh timeout
       FFh invalid handle
Desc:  decrement the semaphore's value, optionally waiting until its value
     becomes positive before decrementing

Note:  this function is supported by NetWare 4.6+, Advanced NetWare 1.0+, and
     Alloy NTNX

See Also: AX=C500h"NetWare",AX=C501h,AX=C503h