Use SECCON to override default secondary console selection

Source/HBIOS/hbios.asm

@@ -2852,19 +2852,27 @@ HB_FP1:
 ;
 HB_FP2:
 	; IF SEC SWITCH IS SET, WE WANT TO BUMP TO SECONDARY
-	; CRT OR SERIAL DEVICE.  FOR NOW, WE ARE GOING TO CHEAT AND
-	; JUST INCREMENT THE CONSOLE DEVICE UNIT.  THIS SHOULD WORK
-	; ASSUMING NORMAL ORDERING OF THE CHARACTER DEVICE UNITS.
+	; CRT OR SERIAL DEVICE. IF AN OVERRIDE IS SPECIFIED USING
+	; SECCON, USE THAT, OTHERWISE INCREMENT THE DEFAULT UNIT.
+	; THIS SHOULD WORK ASSUMING NORMAL ORDERING OF THE
+	; CHARACTER DEVICE UNITS.
 	LD	A,B			; RECOVER SWITCH SETTINGS
 	AND	SW_SEC			; TEST SEC BIT
 	JR	Z,HB_FPZ		; IF NOT SET, THEN ALL DONE
 ;
-	; INCREMENT CONSOLE UNIT, BUT MAKE SURE IT DOES NOT EXCEED
-	; THE HIGHEST CHAR UNIT IN SYSTEM.
 	LD	A,(CIO_CNT)		; GET CHAR UNIT COUNT
 	LD	B,A			; MOVE TO B
+	LD	A,SECCON		; GET SEC CONSOLE SETTING
+	CP	$FF			; $FF MEANS USE INCREMENT
+	JR	NZ,HB_FP3		; BYPASS IF NOT $FF 
+;
+	; INCREMENT CONSOLE UNIT
 	LD	A,(HB_NEWCON)		; GET NEW CONSOLE UNIT
 	INC	A			; BUMP TO SECONDARY
+;
+HB_FP3:
+	; MAKE SURE NEW CONSOLE UNIT DOES NOT EXCEED THE HIGHEST
+	; CHAR UNIT IN SYSTEM.
 	CP	B			; A (UNIT) >= B (CNT)?
 	JR	NC,HB_FPZ		; ABORT IF UNIT TOO HIGH
 	LD	(HB_NEWCON),A		; UPDATE NEW CONSOLE UNIT