Int 14 Fn 15  - PC-mos/386 V5.01 $serial.sys V5.04 - Input String          [S]

   AH = 15h
   CX = size of buffer
   DX = port number
   ES:BX -> buffer for received characters
   SI = timeout in clock ticks or 0000h for default

Return: AX = number of characters actually read
   ZF set on timeout (no data available)

See Also: AH=02h,AH=14h"PC-MOS",AH=16h"PC-MOS"