Int 14 Fn 89  - Comm-drv V14.0 - Turn On Rts                               [S]

   AH = 89h
   DX = port number

Return: AH bit 7 set on error
   AH bit 7 clear if successful

See Also: AX=8000h"COMM-DRV",AH=87h"COMM-DRV",AH=8Ah"COMM-DRV"