diff --git a/Source/HBIOS/uart.asm b/Source/HBIOS/uart.asm
index 52ecd2cf..e38b095f 100644
--- a/Source/HBIOS/uart.asm
+++ b/Source/HBIOS/uart.asm
@@ -47,6 +47,12 @@ UART_EFR		.EQU	2	; LCR=$BF: ENHANCED FEATURE REG (READ/WRITE)
 ;UART_FIFO		.EQU	0	; FIFO ENABLE BIT
 ;UART_AFC		.EQU	1	; AUTO FLOW CONTROL ENABLE BIT
 ;
+UARTSBASE		.EQU	$68
+UARTCBASE		.EQU	$80
+UARTMBASE		.EQU	$48
+UART4BASE		.EQU	$C0
+UARTRBASE		.EQU	$A0
+;
 #DEFINE	UART_INP(RID)	CALL UART_INP_IMP \ .DB RID
 #DEFINE	UART_OUTP(RID)	CALL UART_OUTP_IMP \ .DB RID
 ;
@@ -416,7 +422,7 @@ UART_DETECT2:	; PICK BETWEEN 16550A/C
 ;
 UART_DETECT_NONE:
 	LD	A,(IY + 2)		; BASE IO PORT
-	CP	$68			; IS THIS PRIMARY SBC PORT?
+	CP	UARTSBASE		; IS THIS PRIMARY SBC PORT?
 	JR	Z,UART_DETECT_8250	; SPECIAL CASE FOR PRIMARY UART!
 	LD	A,UART_NONE		; IF SO, TREAT AS 8250 NO MATTER WHAT
 	RET
@@ -591,8 +597,8 @@ UART_CFG:
 	; SBC/ZETA ONBOARD SERIAL PORT
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$68				; IO PORT BASE (RBR, THR)
-	.DB	$68 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UARTSBASE			; IO PORT BASE (RBR, THR)
+	.DB	UARTSBASE + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 #ENDIF
@@ -600,8 +606,8 @@ UART_CFG:
 	; CASSETTE INTERFACE SERIAL PORT
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$80				; IO PORT BASE (RBR, THR)
-	.DB	$80 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UARTCBASE			; IO PORT BASE (RBR, THR)
+	.DB	UARTCBASE + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCASSPD			; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 #ENDIF
@@ -609,8 +615,8 @@ UART_CFG:
 	; MF/PIC SERIAL PORT
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$48				; IO PORT BASE (RBR, THR)
-	.DB	$48 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UARTMBASE			; IO PORT BASE (RBR, THR)
+	.DB	UARTMBASE + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 #ENDIF
@@ -618,29 +624,29 @@ UART_CFG:
 	; 4UART SERIAL PORT A
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$C0				; IO PORT BASE (RBR, THR)
-	.DB	$C0 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UART4BASE+0			; IO PORT BASE (RBR, THR)
+	.DB	UART4BASE+0 + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 	; 4UART SERIAL PORT B
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$C8				; IO PORT BASE (RBR, THR)
-	.DB	$C8 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UART4BASE+8			; IO PORT BASE (RBR, THR)
+	.DB	UART4BASE+8 + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 	; 4UART SERIAL PORT C
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$D0				; IO PORT BASE (RBR, THR)
-	.DB	$D0 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UART4BASE+16			; IO PORT BASE (RBR, THR)
+	.DB	UART4BASE+16 + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 	; 4UART SERIAL PORT D
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$D8				; IO PORT BASE (RBR, THR)
-	.DB	$D8 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UART4BASE+24			; IO PORT BASE (RBR, THR)
+	.DB	UART4BASE+24 + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 #ENDIF
@@ -648,15 +654,15 @@ UART_CFG:
 	; UARTRC SERIAL PORT A
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$A0				; IO PORT BASE (RBR, THR)
-	.DB	$A0 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UARTRBASE			; IO PORT BASE (RBR, THR)
+	.DB	UARTRBASE + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 	; UARTRC SERIAL PORT B
 	.DB	0				; DEVICE NUMBER (UPDATED DURING INIT)
 	.DB	0				; UART TYPE
-	.DB	$A8				; IO PORT BASE (RBR, THR)
-	.DB	$A8 + UART_LSR			; LINE STATUS PORT (LSR)
+	.DB	UARTRBASE+8			; IO PORT BASE (RBR, THR)
+	.DB	UARTRBASE+8 + UART_LSR		; LINE STATUS PORT (LSR)
 	.DW	UARTCFG				; LINE CONFIGURATION
 	.FILL	2,$FF				; FILLER
 #ENDIF