INT 14 - 3com BAPI SERIAL I/O - EN/DISABLE "ENTER COMMAND MODE" (ECM) CHARACTER
	AH = B0h
	AL = new state (00h disabled, 01h enabled)
Return: AH = return code (00h,07h,0Ah) (see #00394)
Note:	disabling the ECM character allows applications to send data which
	  includes the ECM character
SeeAlso: AX=AF00h"BAPI",AH=B1h,AH=B2h