DDT should not read from the %TIFUL channel when %TOFCI isn't set.

Even if %TOFCI isn't set, a %TIFUL channel can return characters with
bucky bits.  A terminal input source such SUPDUP can insert 12-bit
characters with the intelligent terminal protocol, using the ^\ escape
character.

src/sysen1/ddt.1547

@@ -6965,9 +6965,11 @@ TYI:	CALL TYOFRC	;.LISTEN IS SUPPOSED TO FORCE OUTPUT.
 	JUMPE D,CPOPJ
 TYI3:	CALL HAKKAM	;DO HAKKAH RQ'S, SAY DO ANY MORE WHEN QUEUED.
 	SETZM CTLZFL
-	SKIPGE D,TTYUNR
-	  .IOT TYIFC,D	;READ FULL CHAR SET INPUT CHANNEL
-	SKIPE METAP
+	SKIPL D,TTYUNR
+	 JRST TYI4
+	SYSCAL IOT,[TYIC2 ? D]
+	 .VALUE
+TYI4:	SKIPE METAP
 	 JRST [TRZ D,%TXTOP+%TXSUP	;CLEAR TOP AND SUPER
 	       TRZE D,%TXCTL	;IF CONTROL BIT SET,
 	        TRZ D,140	;CONVERT TO ASCII.
@@ -6975,9 +6977,9 @@ TYI3:	CALL HAKKAM	;DO HAKKAH RQ'S, SAY DO ANY MORE WHEN QUEUED.
 		JRST .+1
 	       MOVEM D,TTYUNR	;META BIT SET, SAVE CHAR FOR LATER.
 	       MOVEI D,33	;RETURN ALTMODE.
-	       JRST TYI4]
+	       JRST TYI5]
 	SETOM TTYUNR
-TYI4:	setzm hakok	;defer HAKKAH rq's again.
+TYI5:	setzm hakok	;defer HAKKAH rq's again.
 	skipe echop
 	 pushj p,echo	;Echo character.
 	skipn tthelp		   ;If [HELP] isn't desired
@@ -10592,9 +10594,11 @@ IOCOPN:	TSOPEN TYOC,[[21,,'TTY]]
 	  tlnn i4,%toovr  ;  or can't be overwritten,
 	    setom erase	;   ^PX and friends will win!
 	TLNE I4,%TOFCI	;CAN TTY DO FULL 12-BIT CHARACTER SET?
-	 AOSA METAP	; META KEY WINS
-	  CAIA
-	   AOS ECHOP	; DO ECHOING.
+	 JRST [ AOS METAP	; META KEY WINS
+		AOS ECHOP	; DO ECHOING.
+		MOVEI I3,TYIFC
+		MOVEM I3,TYIC2
+		JRST .+1 ]
 	TLNE I4,%TOMVU
 	 AOS GETTY
 	TLZ C,%TSSAI+%TSROL+%TSMOR
@@ -17630,6 +17634,7 @@ JPDLB:	BLOCK JPDLL
 JPDLE::
 JPDLC:	0		;# OF VALID ENTRIES IN JPDL (BETWEEN 0 AND JPDLL)
 METAP:	0		;WINNING META KEY
+TYIC2:	TYIC		;INPUT CHANNEL FOR TYI
 ECHOP:	0		;DO ECHOING
 
 	VARIAB