diff --git a/Source/HBIOS/cfg_sbc.asm b/Source/HBIOS/cfg_sbc.asm
index 7576fbe1..27de79c6 100644
--- a/Source/HBIOS/cfg_sbc.asm
+++ b/Source/HBIOS/cfg_sbc.asm
@@ -38,6 +38,7 @@ KIOENABLE	.EQU	FALSE		; ENABLE ZILOG KIO SUPPORT
 KIOBASE		.EQU	$80		; KIO BASE I/O ADDRESS
 ;
 CTCENABLE	.EQU	FALSE		; ENABLE ZILOG CTC SUPPORT
+CTCBASE		.EQU	$80		; CTC BASE FOR ECB-ZILOG-PERIPHERALS 
 ;
 DIAGENABLE	.EQU	FALSE		; ENABLES OUTPUT TO 8 BIT LED DIAGNOSTIC PORT
 DIAGPORT	.EQU	$00		; DIAGNOSTIC PORT ADDRESS
diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index b17a35ca..e3e0e75b 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -1071,16 +1071,62 @@ HB_CPU2:
 ;
   #IF (HTIMENABLE)			; SIMH TIMER
 ;
-    #IF (INTMODE == 1)
+    #IF (INTMODE == 1) 
 	LD	HL,HB_TIMINT
 	CALL	HB_ADDIM1		; ADD TO IM1 CALL LIST
     #ENDIF
+
+  #ENDIF
+  #IF (CTCENABLE)
+     #IF (INTMODE == 2)
 ;
-    #IF (INTMODE == 2)
-	;LD	HL,HB_TIMINT
-	;LD	(HBX_IVT),HL
-    #ENDIF
+	; TIMER INTERRUPT IS ON CTCD, VECTOR IS FOURTH IVT SLOT
+	LD	HL,HB_TIMINT		; TIMER INT HANDLER ADR
+	LD	(IVT(INT_CTC0D)),HL	; IVT ENTRY FOR CTC0D
 ;
+	; CTC USES 4 CONSECUTIVE VECTOR POSITIONS, ONE FOR
+	; EACH CHANNEL.  BELOW WE SET THE BASE VECTOR TO THE
+	; START OF THE IVT, SO THE FIRST FOUR ENTIRES OF THE
+	; IVT CORRESPOND TO CTC CHANNELS A-D
+	LD	A,0
+	OUT	(CTCA),A		; SETUP CTC BASE INT VECTOR
+;
+	; ASSUMING ECB-ZP WITH 4.9125MHz XTAL AND / 8 DIVIDER
+	; JUMPER X5 15-16, 9-11, X5 PIN 3 (PHI_X) TO X4 PIN 7 (CTC_TG2)
+	; CONFIGURE CHANNEL D FOR 50HZ PERIODIC INTERRUPTS
+	; CTC CLK = 614,400Hz
+	; CTCD TIME CONSTANT = 48
+	; INT FREQ IS CTC CLK / CTCC TC / CTCD TC
+	; WHICH IS 614,400HZ / 256 / 48 = 50HZ
+	LD	A,%01010111		; CTCC CONTROL WORD VALUE
+		;  |||||||+-- 1=CONTROL WORD FLAG
+		;  ||||||+--- 1=SOFTWARE RESET
+		;  |||||+---- 1=TIME CONSTANT FOLLOWS
+		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
+		;  |||+------ 1=RISING EDGE TRIGGER
+		;  ||+------- 1=PRESCALER OF 16 (NOT USED)
+		;  |+-------- 1=COUNTER MODE
+		;  +--------- 0=NO INTERRUPTS
+	OUT	(CTCC),A		; SETUP CTCC
+	LD	A,0			; CTCC TIMER CONSTANT = 256, 0 MEANS 256
+	OUT	(CTCC),A		; SETUP CTCC TIMER CONSTANT
+	LD	A,%11010111		; CTCD CONTROL WORD VALUE
+		;  |||||||+-- 1=CONTROL WORD FLAG
+		;  ||||||+--- 1=SOFTWARE RESET
+		;  |||||+---- 1=TIME CONSTANT FOLLOWS
+		;  ||||+----- 0=AUTO TRIGGER WHEN TIME CONST LOADED
+		;  |||+------ 1=RISING EDGE TRIGGER
+		;  ||+------- 1=PRESCALER OF 16 (NOT USED)
+		;  |+-------- 1=COUNTER MODE
+		;  +--------- 1=ENABLE INTERRUPTS
+	OUT	(CTCD),A		; SETUP CTCD
+	LD	A,48			; CTCD TIMER CONSTANT = 48
+	OUT	(CTCD),A		; SETUP CTCD TIMER CONSTANT
+
+     #ELSE
+	.ECHO	"*** ERROR: CTC REQUIRES INTMODE 2!!!\n"
+	!!!	; FORCE AN ASSEMBLY ERROR
+     #ENDIF
   #ENDIF
 ;
 #ENDIF
@@ -1740,6 +1786,9 @@ HB_INITTBL:
 #IF (UFENABLE)
 	.DW	UF_INIT
 #ENDIF
+#IF (CTCENABLE)
+	.DW	CTC_INIT
+#ENDIF
 ;
 HB_INITTBLLEN	.EQU	(($ - HB_INITTBL) / 2)
 ;
@@ -3197,6 +3246,14 @@ SIZ_UF	.EQU	$ - ORG_UF
 		.ECHO	SIZ_UF
 		.ECHO	" bytes.\n"
 #ENDIF
+#IF (CTCENABLE)
+ORG_CTC	.EQU	$
+  #INCLUDE "ctcstub.asm"
+SIZ_CTC	.EQU	$ - ORG_CTC
+		.ECHO	"CTC occupies "
+		.ECHO	SIZ_CTC
+		.ECHO	" bytes.\n"
+#ENDIF
 ;
 #DEFINE USEDELAY
 #INCLUDE "util.asm"