diff --git a/sio.asm b/sio.asm
new file mode 100644
index 00000000..75ccdaf3
--- /dev/null
+++ b/sio.asm
@@ -0,0 +1,921 @@
+;
+;==================================================================================================
+; SIO DRIVER (SERIAL PORT)
+;==================================================================================================
+;
+;  SETUP PARAMETER WORD:
+;  +-------+---+-------------------+ +---+---+-----------+---+-------+
+;  |       |RTS| ENCODED BAUD RATE | |DTR|XON|  PARITY   |STP| 8/7/6 |
+;  +-------+---+---+---------------+ ----+---+-----------+---+-------+
+;    F   E   D   C   B   A   9   8     7   6   5   4   3   2   1   0
+;       -- MSB (D REGISTER) --           -- LSB (E REGISTER) --
+;
+;               
+SIO_NONE	.EQU	0
+SIO_SIO		.EQU	1
+;               
+#IF (SIOMODE == SIOMODE_RC)
+SIOA_CMD	.EQU	SIOBASE + $00      ;PS	
+SIOA_DAT	.EQU	SIOBASE + $01      ;PS 
+SIOB_CMD	.EQU	SIOBASE + $02      ;PS 
+SIOB_DAT	.EQU	SIOBASE + $03      ;PS
+SIO_WR4		.EQU	$C4		            ;PS  CLK/64=115200 BAUD, NO PARITY, 1 STOP BIT ; 11000100 11=*64 00=8bit sync character 01=1 stop bit 0 = parity even/odd 0=parity disabled
+#ENDIF
+;
+#IF (SIOMODE == SIOMODE_SMB)
+SIOA_CMD	.EQU	SIOBASE + $02      ;PS
+SIOA_DAT	.EQU	SIOBASE + $00      ;PS
+SIOB_CMD	.EQU	SIOBASE + $03      ;PS
+SIOB_WR4	.EQU	SIOBASE + $01      ;PS
+SIO_CFG		.EQU	$C4		            ;PS CLK/64=115200 BAUD, NO PARITY, 1 STOP BIT ; 11000100 11=*64 00=8bit sync character 01=1 stop bit 0 = parity even/odd 0=parity disabled
+#ENDIF
+;
+#IF (SIOMODE == SIOMODE_ZP)	;PS	
+SIOA_CMD	.EQU	SIOBASE + $06		;PS
+SIOA_DAT	.EQU	SIOBASE + $04		;PS 
+SIOB_CMD	.EQU	SIOBASE + $07		;PS 
+SIOB_DAT	.EQU	SIOBASE + $05		;PS 
+SIO_WR4		.EQU	$44		            ;PS CLK/16=38400 BAUD, NO PARITY, 1 STOP BIT ; PS 01000100 10=*16 00=8bit sync character 01=1 stop bit 0 = parity even/odd 0=parity disabled
+#ENDIF						            ;PS 
+;
+
+#IF (DEFSIOCLK/DEFSIODIV/1 ==     75) 
+SIOBAUD1 .EQU  0 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==    150) 
+SIOBAUD1 .EQU  1 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==    300) 
+SIOBAUD1  .EQU  2 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==    600) 
+SIOBAUD1  .EQU  3 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==   1200) 
+SIOBAUD1  .EQU  4 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==   2400) 
+SIOBAUD1  .EQU  5 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==   4800) 
+SIOBAUD1  .EQU  6 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==   9600) 
+SIOBAUD1  .EQU  7 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==  19200) 
+SIOBAUD1  .EQU  8 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==  38400) 
+SIOBAUD1  .EQU  9 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==  76800) 
+SIOBAUD1  .EQU 10 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 == 153600) 
+SIOBAUD1  .EQU 11 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 == 307200) 
+SIOBAUD1  .EQU 12 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 == 614400) 
+SIOBAUD1  .EQU 13 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 =1228800) 
+SIOBAUD1  .EQU 14 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 =2457600) 
+SIOBAUD1  .EQU 15 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==    225) 
+SIOBAUD1  .EQU 16 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==    450) 
+SIOBAUD1  .EQU 17 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==    900) 
+SIOBAUD1  .EQU 18 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==   1800) 
+SIOBAUD1  .EQU 19 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==   3600) 
+SIOBAUD1  .EQU 20 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==   7200) 
+SIOBAUD1  .EQU 21 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==  14400) 
+SIOBAUD1  .EQU 22 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==  28800) 
+SIOBAUD1  .EQU 23 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 ==  57600) 
+SIOBAUD1  .EQU 24 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 == 115200) 
+SIOBAUD1  .EQU 25 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 == 230400) 
+SIOBAUD1  .EQU 26 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 == 921600) 
+SIOBAUD1  .EQU 28 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 =1843200) 
+SIOBAUD1  .EQU 29 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 =3686400) 
+SIOBAUD1  .EQU 30 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/1 =7372800) 
+SIOBAUD1  .EQU 31 
+#ENDIF
+
+
+#IF (DEFSIOCLK/DEFSIODIV/16 ==     75) 
+SIOBAUD1 .EQU  0 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==    150) 
+SIOBAUD2  .EQU  1 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==    300) 
+SIOBAUD2  .EQU  2 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==    600) 
+SIOBAUD2  .EQU  3 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==   1200) 
+SIOBAUD2  .EQU  4 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==   2400) 
+SIOBAUD2  .EQU  5 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==   4800) 
+SIOBAUD2  .EQU  6 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==   9600) 
+SIOBAUD2  .EQU  7 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==  19200) 
+SIOBAUD2  .EQU  8 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==  38400) 
+SIOBAUD2  .EQU  9 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==  76800) 
+SIOBAUD2  .EQU 10 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 == 153600) 
+SIOBAUD2  .EQU 11 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 == 307200) 
+SIOBAUD2  .EQU 12 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 == 614400) 
+SIOBAUD2  .EQU 13 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 =1228800) 
+SIOBAUD2  .EQU 14 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 =2457600) 
+SIOBAUD2  .EQU 15 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==    225) 
+SIOBAUD2  .EQU 16 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==    450) 
+SIOBAUD2  .EQU 17 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==    900) 
+SIOBAUD2  .EQU 18 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==   1800) 
+SIOBAUD2  .EQU 19 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==   3600) 
+SIOBAUD2  .EQU 20 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==   7200) 
+SIOBAUD2  .EQU 21 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==  14400) 
+SIOBAUD2  .EQU 22 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==  28800) 
+SIOBAUD2  .EQU 23 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==  57600) 
+SIOBAUD2  .EQU 24 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 == 115200) 
+SIOBAUD2  .EQU 25 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 == 230400) 
+SIOBAUD2  .EQU 26 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 == 460800) 
+SIOBAUD2  .EQU 27 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 == 921600) 
+SIOBAUD2  .EQU 28 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==1843200) 
+SIOBAUD2  .EQU 29 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==3686400) 
+SIOBAUD2  .EQU 30 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/16 ==7372800) 
+SIOBAUD2  .EQU 31 
+#ENDIF
+
+#IF (DEFSIOCLK/DEFSIODIV/32==     75) 
+SIOBAUD3  .EQU  0 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==    150) 
+SIOBAUD3  .EQU  1 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==    300) 
+SIOBAUD3  .EQU  2 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==    600) 
+SIOBAUD3  .EQU  3 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==   1200) 
+SIOBAUD3  .EQU  4 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==   2400) 
+SIOBAUD3  .EQU  5 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==   4800) 
+SIOBAUD3  .EQU  6 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==   9600) 
+SIOBAUD3  .EQU  7 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==  19200) 
+SIOBAUD3  .EQU  8 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==  38400) 
+SIOBAUD3  .EQU  9 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==  76800) 
+SIOBAUD3  .EQU 10 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32== 153600) 
+SIOBAUD3  .EQU 11 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32== 307200) 
+SIOBAUD3  .EQU 12 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32== 614400) 
+SIOBAUD3  .EQU 13 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==1228800) 
+SIOBAUD3  .EQU 14 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==2457600) 
+SIOBAUD3  .EQU 15 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==    225) 
+SIOBAUD3  .EQU 16 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==    450) 
+SIOBAUD3  .EQU 17 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==    900) 
+SIOBAUD3  .EQU 18 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==   1800) 
+SIOBAUD3  .EQU 19 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==   3600) 
+SIOBAUD3  .EQU 20 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==   7200) 
+SIOBAUD3  .EQU 21 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==  14400) 
+SIOBAUD3  .EQU 22 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==  28800) 
+SIOBAUD3  .EQU 23 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==  57600) 
+SIOBAUD3  .EQU 24 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32= 115200) 
+SIOBAUD3  .EQU 25 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32= 230400) 
+SIOBAUD3  .EQU 26 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32== 460800) 
+SIOBAUD3  .EQU 27 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32== 921600) 
+SIOBAUD3  .EQU 28 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==1843200) 
+SIOBAUD3  .EQU 29 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==3686400) 
+SIOBAUD3  .EQU 30 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/32==7372800) 
+SIOBAUD3  .EQU 31 
+#ENDIF
+
+#IF (DEFSIOCLK/DEFSIODIV/64==     75) 
+SIOBAUD4  .EQU  0 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==    150) 
+SIOBAUD4  .EQU  1 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==    300) 
+SIOBAUD4  .EQU  2 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==    600) 
+SIOBAUD4  .EQU  3 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==   1200) 
+SIOBAUD4  .EQU  4 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==   2400) 
+SIOBAUD4  .EQU  5 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==   4800) 
+SIOBAUD4  .EQU  6 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==  9600) 
+SIOBAUD4  .EQU  7 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==  19200) 
+SIOBAUD4  .EQU  8 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==  38400) 
+SIOBAUD4  .EQU  9 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==  76800) 
+SIOBAUD4  .EQU 10 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64== 153600) 
+SIOBAUD4  .EQU 11 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64== 307200) 
+SIOBAUD4  .EQU 12 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64== 614400) 
+SIOBAUD4  .EQU 13 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==1228800) 
+SIOBAUD4  .EQU 14 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==2457600) 
+SIOBAUD4  .EQU 15 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==    225) 
+SIOBAUD4  .EQU 16 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==    450) 
+SIOBAUD4  .EQU 17 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==    900) 
+SIOBAUD4  .EQU 18 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==   1800) 
+SIOBAUD4  .EQU 19 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==   3600) 
+SIOBAUD4  .EQU 20 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==   7200) 
+SIOBAUD4  .EQU 21 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==  14400) 
+SIOBAUD4  .EQU 22 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==  28800) 
+SIOBAUD4  .EQU 23 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==  57600) 
+SIOBAUD4  .EQU 24 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64== 115200) 
+SIOBAUD4  .EQU 25 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64== 230400) 
+SIOBAUD4  .EQU 26 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64== 460800) 
+SIOBAUD4  .EQU 27 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64== 921600) 
+SIOBAUD4  .EQU 28 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==1843200) 
+SIOBAUD4  .EQU 29 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==3686400) 
+SIOBAUD4  .EQU 30 
+#ENDIF
+#IF (DEFSIOCLK/DEFSIODIV/64==7372800) 
+SIOBAUD4  .EQU 31 
+#ENDIF
+
+;
+SIO_PREINIT:
+;
+; SETUP THE DISPATCH TABLE ENTRIES
+;
+	LD	B,SIO_CNT		; LOOP CONTROL
+	LD	C,0			; PHYSICAL UNIT INDEX
+	XOR	A			; ZERO TO ACCUM
+	LD	(SIO_DEV),A		; CURRENT DEVICE NUMBER
+SIO_PREINIT0:	
+	PUSH	BC			; SAVE LOOP CONTROL
+	LD	A,C			; PHYSICAL UNIT TO A
+	RLCA				; MULTIPLY BY CFG TABLE ENTRY SIZE (8 BYTES)
+	RLCA				; ...
+	RLCA				; ... TO GET OFFSET INTO CFG TABLE
+	LD	HL,SIO_CFG		; POINT TO START OF CFG TABLE
+	CALL	ADDHLA			; HL := ENTRY ADDRESS
+	PUSH	HL			; SAVE IT
+	PUSH	HL			; COPY CFG DATA PTR
+	POP	IY			; ... TO IY
+	CALL	SIO_INITUNIT		; HAND OFF TO GENERIC INIT CODE
+	POP	DE			; GET ENTRY ADDRESS BACK, BUT PUT IN DE
+	POP	BC			; RESTORE LOOP CONTROL
+;
+	LD	A,(IY + 1)		; GET THE SIO TYPE DETECTED
+	OR	A			; SET FLAGS
+	JR	Z,SIO_PREINIT2		; SKIP IT IF NOTHING FOUND
+;	
+	PUSH	BC			; SAVE LOOP CONTROL
+	LD	BC,SIO_FNTBL		; BC := FUNCTION TABLE ADDRESS
+	CALL	NZ,CIO_ADDENT		; ADD ENTRY IF SIO FOUND, BC:DE
+	POP	BC			; RESTORE LOOP CONTROL
+;
+SIO_PREINIT2:	
+	INC	C			; NEXT PHYSICAL UNIT
+	DJNZ	SIO_PREINIT0		; LOOP UNTIL DONE
+;
+#IF (INTMODE == 1)
+	; ADD IM1 INT CALL LIST ENTRY IF APPROPRIATE
+	LD	A,(SIO_DEV)		; GET NEXT DEVICE NUM
+	OR	A			; SET FLAGS
+	JR	Z,SIO_PREINIT3		; IF ZERO, NO SIO DEVICES
+	LD	HL,SIO_INT		; GET INT VECTOR
+	CALL	HB_ADDIM1		; ADD TO IM1 CALL LIST
+#ENDIF
+;
+#IF (INTMODE == 2)
+	; SETUP SIO INTERRUPT VECTOR IN IVT
+	LD	HL,INT_SIO
+	LD	(HBX_IVT + IVT_SER0),HL
+#ENDIF
+;
+SIO_PREINIT3:
+	XOR	A			; SIGNAL SUCCESS
+	RET				; AND RETURN
+;
+; SIO INITIALIZATION ROUTINE
+;
+SIO_INITUNIT:
+	CALL	SIO_DETECT		; DETERMINE SIO TYPE
+	LD	(IY + 1),A		; SAVE IN CONFIG TABLE
+	OR	A			; SET FLAGS
+	RET	Z			; ABORT IF NOTHING THERE
+
+	; UPDATE WORKING SIO DEVICE NUM
+	LD	HL,SIO_DEV		; POINT TO CURRENT UART DEVICE NUM
+	LD	A,(HL)			; PUT IN ACCUM
+	INC	(HL)			; INCREMENT IT (FOR NEXT LOOP)
+	LD	(IY),A			; UDPATE UNIT NUM
+	
+	; SET DEFAULT CONFIG
+	LD	DE,-1			; LEAVE CONFIG ALONE
+	JP	SIO_INITDEV		; IMPLEMENT IT AND RETURN
+;
+;
+;
+SIO_INIT:
+	LD	B,SIO_CNT		; COUNT OF POSSIBLE SIO UNITS
+	LD	C,0			; INDEX INTO SIO CONFIG TABLE
+SIO_INIT1:
+	PUSH	BC			; SAVE LOOP CONTROL
+	
+	LD	A,C			; PHYSICAL UNIT TO A
+	RLCA				; MULTIPLY BY CFG TABLE ENTRY SIZE (8 BYTES)
+	RLCA				; ...
+	RLCA				; ... TO GET OFFSET INTO CFG TABLE
+	LD	HL,SIO_CFG		; POINT TO START OF CFG TABLE
+	CALL	ADDHLA			; HL := ENTRY ADDRESS
+	PUSH	HL			; COPY CFG DATA PTR
+	POP	IY			; ... TO IY
+	
+	LD	A,(IY + 1)		; GET SIO TYPE
+	OR	A			; SET FLAGS
+	CALL	NZ,SIO_PRTCFG		; PRINT IF NOT ZERO
+	
+	POP	BC			; RESTORE LOOP CONTROL
+	INC	C			; NEXT UNIT
+	DJNZ	SIO_INIT1		; LOOP TILL DONE
+;
+	XOR	A			; SIGNAL SUCCESS
+	RET				; DONE
+;
+; INTERRUPT HANDLER
+;
+SIO_INT:
+SIOA_INT:
+	; CHECK FOR RECEIVE PENDING ON CHANNEL A
+	XOR	A			; A := 0
+	OUT	(SIOA_CMD),A		; ADDRESS RD0
+	IN	A,(SIOA_CMD)		; GET RD0
+	AND	$01			; ISOLATE RECEIVE READY BIT
+	JR	Z,SIOB_INT		; CHECK CHANNEL B
+;
+SIOA_INT00:
+	; HANDLE CHANNEL A
+	IN	A,(SIOA_DAT)		; READ PORT
+	LD	E,A			; SAVE BYTE READ
+	LD	A,(SIOA_CNT)		; GET CURRENT BUFFER USED COUNT
+	CP	SIOA_BUFSZ		; COMPARE TO BUFFER SIZE
+	RET	Z			; BAIL OUT IF BUFFER FULL, RCV BYTE DISCARDED
+	INC	A			; INCREMENT THE COUNT
+	LD	(SIOA_CNT),A		; AND SAVE IT
+	CP	SIOA_BUFSZ - 5		; BUFFER GETTING FULL?
+	JR	NZ,SIOA_INT0		; IF NOT, BYPASS CLEARING RTS
+	LD	A,5			; RTS IS IN WR5
+	OUT	(SIOA_CMD),A		; ADDRESS WR5
+	LD	A,$E8			; VALUE TO CLEAR RTS
+	OUT	(SIOA_CMD),A		; DO IT
+SIOA_INT0:
+	LD	HL,(SIOA_HD)		; GET HEAD POINTER
+	LD	A,L			; GET LOW BYTE
+	CP	SIOA_BUFEND & $FF	; PAST END?
+	JR	NZ,SIOA_INT1		; IF NOT, BYPASS POINTER RESET
+	LD	HL,SIOA_BUF		; ... OTHERWISE, RESET TO START OF BUFFER
+SIOA_INT1:
+	LD	A,E			; RECOVER BYTE READ
+	LD	(HL),A			; SAVE RECEIVED BYTE TO HEAD POSITION
+	INC	HL			; INCREMENT HEAD POINTER
+	LD	(SIOA_HD),HL		; SAVE IT
+;
+	; CHECK FOR MORE PENDING...
+	XOR	A			; A := 0
+	OUT	(SIOA_CMD),A		; ADDRESS RD0
+	IN	A,(SIOA_CMD)		; GET RD0
+	RRA				; READY BIT TO CF
+	JR	C,SIOA_INT00		; IF SET, DO SOME MORE
+	OR	$FF			; NZ SET TO INDICATE INT HANDLED
+	RET				; AND RETURN
+;
+SIOB_INT:
+	; CHECK FOR RECEIVE PENDING ON CHANNEL B
+	XOR	A			; A := 0
+	OUT	(SIOB_CMD),A		; ADDRESS RD0
+	IN	A,(SIOB_CMD)		; GET RD0
+	AND	$01			; ISOLATE RECEIVE READY BIT
+	RET	Z			; IF NOT, RETURN WITH Z SET
+;
+SIOB_INT00:
+	; HANDLE CHANNEL B
+	IN	A,(SIOB_DAT)		; READ PORT
+	LD	E,A			; SAVE BYTE READ
+	LD	A,(SIOB_CNT)		; GET CURRENT BUFFER USED COUNT
+	CP	SIOB_BUFSZ		; COMPARE TO BUFFER SIZE
+	RET	Z			; BAIL OUT IF BUFFER FULL, RCV BYTE DISCARDED
+	INC	A			; INCREMENT THE COUNT
+	LD	(SIOB_CNT),A		; AND SAVE IT
+	CP	SIOB_BUFSZ - 5		; BUFFER GETTING FULL?
+	JR	NZ,SIOB_INT0		; IF NOT, BYPASS CLEARING RTS
+	LD	A,5			; RTS IS IN WR5
+	OUT	(SIOB_CMD),A		; ADDRESS WR5
+	LD	A,$E8			; VALUE TO CLEAR RTS
+	OUT	(SIOB_CMD),A		; DO IT
+SIOB_INT0:
+	LD	HL,(SIOB_HD)		; GET HEAD POINTER
+	LD	A,L			; GET LOW BYTE
+	CP	SIOB_BUFEND & $FF	; PAST END?
+	JR	NZ,SIOB_INT1		; IF NOT, BYPASS POINTER RESET
+	LD	HL,SIOB_BUF		; ... OTHERWISE, RESET TO START OF BUFFER
+SIOB_INT1:
+	LD	A,E			; RECOVER BYTE READ
+	LD	(HL),A			; SAVE RECEIVED BYTE TO HEAD POSITION
+	INC	HL			; INCREMENT HEAD POINTER
+	LD	(SIOB_HD),HL		; SAVE IT
+;
+	; CHECK FOR MORE PENDING...
+	XOR	A			; A := 0
+	OUT	(SIOB_CMD),A		; ADDRESS RD0
+	IN	A,(SIOB_CMD)		; GET RD0
+	RRA				; READY BIT TO CF
+	JR	C,SIOB_INT00		; IF SET, DO SOME MORE
+	OR	$FF			; NZ SET TO INDICATE INT HANDLED
+	RET				; AND RETURN
+;
+; DRIVER FUNCTION TABLE
+;
+SIO_FNTBL:
+	.DW	SIO_IN
+	.DW	SIO_OUT
+	.DW	SIO_IST
+	.DW	SIO_OST
+	.DW	SIO_INITDEV
+	.DW	SIO_QUERY
+	.DW	SIO_DEVICE
+#IF (($ - SIO_FNTBL) != (CIO_FNCNT * 2))
+	.ECHO	"*** INVALID SIO FUNCTION TABLE ***\n"
+#ENDIF
+;
+;
+;
+SIO_IN:
+	LD	A,(IY + 2)		; GET CHANNEL
+	OR	A			; SET FLAGS
+	JR	Z,SIOA_IN		; HANDLE CHANNEL A
+	DEC	A			; TEST FOR NEXT DEVICE
+	JR	Z,SIOB_IN		; HANDLE CHANNEL B
+	CALL 	PANIC			; ELSE FATAL ERROR
+	RET				; ... AND RETURN
+;
+SIOA_IN:
+	CALL	SIOA_IST		; RECEIVED CHAR READY?
+	JR	Z,SIOA_IN		; LOOP TILL WE HAVE SOMETHING IN BUFFER
+	HB_DI				; AVOID COLLISION WITH INT HANDLER
+	LD	A,(SIOA_CNT)		; GET COUNT
+	DEC	A			; DECREMENT COUNT
+	LD	(SIOA_CNT),A		; SAVE SAVE IT
+	CP	5			; BUFFER LOW THRESHOLD
+	JR	NZ,SIOA_IN0		; IF NOT, BYPASS SETTING RTS
+	LD	A,5			; RTS IS IN WR5
+	OUT	(SIOA_CMD),A		; ADDRESS WR5
+	LD	A,$EA			; VALUE TO SET RTS
+	OUT	(SIOA_CMD),A		; DO IT
+SIOA_IN0:
+	LD	HL,(SIOA_TL)		; GET BUFFER TAIL POINTER
+	LD	E,(HL)			; GET BYTE
+	INC	HL			; BUMP TAIL POINTER
+	LD	A,L			; GET LOW BYTE
+	CP	SIOA_BUFEND & $FF	; PAST END?
+	JR	NZ,SIOA_IN1		; IF NOT, BYPASS POINTER RESET
+	LD	HL,SIOA_BUF		; ... OTHERWISE, RESET TO START OF BUFFER
+SIOA_IN1:
+	LD	(SIOA_TL),HL		; SAVE UPDATED TAIL POINTER
+	HB_EI				; INTERRUPTS OK AGAIN
+	XOR	A			; SIGNAL SUCCESS
+	RET				; AND DONE
+;
+SIOB_IN:
+	CALL	SIOB_IST		; RECEIVED CHAR READY?
+	JR	Z,SIOB_IN		; LOOP TILL WE HAVE SOMETHING IN BUFFER
+	HB_DI				; AVOID COLLISION WITH INT HANDLER
+	LD	A,(SIOB_CNT)		; GET COUNT
+	DEC	A			; DECREMENT COUNT
+	LD	(SIOB_CNT),A		; SAVE SAVE IT
+	CP	5			; BUFFER LOW THRESHOLD
+	JR	NZ,SIOB_IN0		; IF NOT, BYPASS SETTING RTS
+	LD	A,5			; RTS IS IN WR5
+	OUT	(SIOB_CMD),A		; ADDRESS WR5
+	LD	A,$EA			; VALUE TO SET RTS
+	OUT	(SIOB_CMD),A		; DO IT
+SIOB_IN0:
+	LD	HL,(SIOB_TL)		; GET BUFFER TAIL POINTER
+	LD	E,(HL)			; GET BYTE
+	INC	HL			; BUMP TAIL POINTER
+	LD	A,L			; GET LOW BYTE
+	CP	SIOB_BUFEND & $FF	; PAST END?
+	JR	NZ,SIOB_IN1		; IF NOT, BYPASS POINTER RESET
+	LD	HL,SIOB_BUF		; ... OTHERWISE, RESET TO START OF BUFFER
+SIOB_IN1:
+	LD	(SIOB_TL),HL		; SAVE UPDATED TAIL POINTER
+	HB_EI				; INTERRUPTS OK AGAIN
+	XOR	A			; SIGNAL SUCCESS
+	RET				; AND DONE
+;
+;
+;
+SIO_OUT:
+	CALL	SIO_OST			; READY FOR CHAR?
+	JR	Z,SIO_OUT		; LOOP IF NOT
+	LD	C,(IY + 3)		; C := SIO CMD PORT
+#IF (SIOMODE == SIOMODE_RC)
+	INC	C			; BUMP TO DATA PORT
+#ENDIF
+#IF (SIOMODE == SIOMODE_SMB)
+	DEC C			; DECREMENT CMD PORT TWICE TO GET DATA PORT
+	DEC C
+#ENDIF
+#IF (SIOMODE == SIOMODE_ZP)
+	DEC C			; DECREMENT CMD PORT TWICE TO GET DATA PORT
+	DEC C
+#ENDIF
+	OUT	(C),E			; SEND CHAR FROM E
+	XOR	A			; SIGNAL SUCCESS
+	RET
+;
+;
+;
+SIO_IST:
+	LD	A,(IY + 2)		; GET CHANNEL
+	OR	A			; SET FLAGS
+	JR	Z,SIOA_IST		; HANDLE CHANNEL A
+	DEC	A			; TEST FOR NEXT DEVICE
+	JR	Z,SIOB_IST		; HANDLE CHANNEL B
+	CALL 	PANIC			; ELSE FATAL ERROR
+	RET				; ... AND RETURN
+;
+SIOA_IST:
+	LD	A,(SIOA_CNT)		; GET BUFFER UTILIZATION COUNT
+	OR	A			; SET FLAGS
+	JP	Z,CIO_IDLE		; NOT READY, RETURN VIA IDLE PROCESSING
+	RET				; AND DONE
+;
+SIOB_IST:
+	LD	A,(SIOB_CNT)		; GET BUFFER UTILIZATION COUNT
+	OR	A			; SET FLAGS
+	JP	Z,CIO_IDLE		; NOT READY, RETURN VIA IDLE PROCESSING
+	RET				; DONE
+;
+;
+;
+SIO_OST:
+	LD	C,(IY + 3)		; CMD PORT
+	XOR	A			; WR0
+	OUT	(C),A			; DO IT
+	IN	A,(C)			; GET STATUS
+	AND	$04			; ISOLATE BIT 2 (TX EMPTY)
+	JP	Z,CIO_IDLE		; NOT READY, RETURN VIA IDLE PROCESSING
+	XOR	A			; ZERO ACCUM
+	INC	A			; ACCUM := 1 TO SIGNAL 1 BUFFER POSITION
+	RET				; DONE
+;
+;
+;
+SIO_INITDEV:
+	HB_DI				; AVOID CONFLICTS
+;
+	; PROGRAM THE SIO/2 CHIP CHANNEL
+	LD	C,(IY + 3)		; COMMAND PORT
+	LD	HL,SIO_INITVALS		; POINT TO INIT VALUES
+	LD	B,SIO_INITLEN		; COUNT OF BYTES TO WRITE
+	OTIR				; WRITE ALL VALUES
+;
+	; RESET THE RECEIVE BUFFER
+	LD	E,(IY + 6)
+	LD	D,(IY + 7)		; DE := _CNT
+	XOR	A			; A := 0
+	LD	(DE),A			; _CNT = 0
+	INC	DE			; DE := ADR OF _HD
+	PUSH	DE			; SAVE IT
+	INC	DE
+	INC	DE
+	INC	DE
+	INC	DE			; DE := ADR OF _BUF
+	POP	HL			; HL := ADR OF _HD
+	LD	(HL),E
+	INC	HL
+	LD	(HL),D			; _HD := _BUF
+	INC	HL
+	LD	(HL),E
+	INC	HL
+	LD	(HL),D			; _TL := _BUF
+;
+	HB_EI				; READY FOR INTS AGAIN
+	XOR	A			; SIGNAL SUCCESS
+	RET				; RETURN
+;
+;
+SIO_INITVALS:
+	.DB	$00, $18	; WR0: CHANNEL RESET
+	.DB	$04, $SIO_WR4	; WR4:  CLK BAUD PARITY STOP BIT ; PST
+	.DB	$01, $18	; WR1: INTERRUPT ON ALL RECEIVE CHARACTERS
+	.DB	$02, IVT_SER0	; WR2: INTERRUPT VECTOR OFFSET
+	.DB	$03, $C1	; WR3: 8 BIT RCV, RX ENABLE
+	.DB	$05, $EA	; WR5: DTR, 8 BITS SEND,  TX ENABLE, RTS
+SIO_INITLEN	.EQU	$ - SIO_INITVALS
+;
+;
+;
+SIO_QUERY:
+	LD	E,(IY + 4)		; FIRST CONFIG BYTE TO E
+	LD	D,(IY + 5)		; SECOND CONFIG BYTE TO D
+	XOR	A			; SIGNAL SUCCESS
+	RET				; DONE
+;
+;
+;
+SIO_DEVICE:
+	LD	D,CIODEV_SIO	; D := DEVICE TYPE
+	LD	E,(IY)		; E := PHYSICAL UNIT
+	XOR	A		; SIGNAL SUCCESS
+	RET
+;
+; SIO DETECTION ROUTINE
+;
+SIO_DETECT:
+	LD	C,(IY + 3)	; COMMAND PORT
+	XOR	A
+	OUT	(C),A		; ACCESS RD0
+	IN	A,(C)		; GET RD0 VALUE
+	LD	B,A		; SAVE IT
+	LD	A,1
+	OUT	(C),A		; ACCESS RD1
+	IN	A,(C)		; GET RD1 VALUE
+	CP	B		; COMPARE
+	LD	A,SIO_NONE	; ASSUME NOTHING THERE
+	RET	Z		; RD0=RD1 MEANS NOTHING THERE
+	LD	A,SIO_SIO	; GUESS WE HAVE A VALID SIO HERE
+	RET			; DONE
+;
+;
+;
+SIO_PRTCFG:
+	; ANNOUNCE PORT
+	CALL	NEWLINE			; FORMATTING
+	PRTS("SIO$")			; FORMATTING
+	LD	A,(IY)			; DEVICE NUM
+	CALL	PRTDECB			; PRINT DEVICE NUM
+	PRTS(": IO=0x$")		; FORMATTING
+	LD	A,(IY + 3)		; GET BASE PORT
+	CALL	PRTHEXBYTE		; PRINT BASE PORT
+
+	; PRINT THE SIO TYPE
+	CALL	PC_SPACE		; FORMATTING
+	LD	A,(IY + 1)		; GET SIO TYPE BYTE
+	RLCA				; MAKE IT A WORD OFFSET
+	LD	HL,SIO_TYPE_MAP		; POINT HL TO TYPE MAP TABLE
+	CALL	ADDHLA			; HL := ENTRY
+	LD	E,(HL)			; DEREFERENCE
+	INC	HL			; ...
+	LD	D,(HL)			; ... TO GET STRING POINTER
+	CALL	WRITESTR		; PRINT IT
+;
+	; ALL DONE IF NO SIO WAS DETECTED
+	LD	A,(IY + 1)		; GET SIO TYPE BYTE
+	OR	A			; SET FLAGS
+	RET	Z			; IF ZERO, NOT PRESENT
+;
+	PRTS(" MODE=$")			; FORMATTING
+	LD	E,(IY + 4)		; LOAD CONFIG
+	LD	D,(IY + 5)		; ... WORD TO DE
+	CALL	PS_PRTSC0		; PRINT CONFIG
+;
+	XOR	A
+	RET
+;
+;
+;
+SIO_TYPE_MAP:
+		.DW	SIO_STR_NONE
+		.DW	SIO_STR_SIO
+
+SIO_STR_NONE	.DB	"<NOT PRESENT>$"
+SIO_STR_SIO	.DB	"SIO$"
+;
+; WORKING VARIABLES
+;
+SIO_DEV		.DB	0		; DEVICE NUM USED DURING INIT
+;
+; CHANNEL A RECEIVE BUFFER
+SIOA_RCVBUF:
+SIOA_CNT	.DB	0		; CHARACTERS IN RING BUFFER
+SIOA_HD		.DW	SIOA_BUF	; BUFFER HEAD POINTER
+SIOA_TL		.DW	SIOA_BUF	; BUFFER TAIL POINTER
+SIOA_BUF	.FILL	32,0		; RECEIVE RING BUFFER
+SIOA_BUFEND	.EQU	$		; END OF BUFFER
+SIOA_BUFSZ	.EQU	$ - SIOA_BUF	; SIZE OF RING BUFFER
+;
+; CHANNEL B RECEIVE BUFFER
+SIOB_RCVBUF:
+SIOB_CNT	.DB	0		; CHARACTERS IN RING BUFFER
+SIOB_HD		.DW	SIOB_BUF	; BUFFER HEAD POINTER
+SIOB_TL		.DW	SIOB_BUF	; BUFFER TAIL POINTER
+SIOB_BUF	.FILL	32,0		; RECEIVE RING BUFFER
+SIOB_BUFEND	.EQU	$		; END OF BUFFER
+SIOB_BUFSZ	.EQU	$ - SIOB_BUF	; SIZE OF RING BUFFER
+;
+; SIO PORT TABLE
+;
+SIO_CFG:
+	; SIO/2 CHANNEL A
+	.DB	0			; DEVICE NUMBER (SET DURING INIT)
+	.DB	0			; SIO TYPE (SET DURING INIT)
+	.DB	0			; SIO CHANNEL (A)
+	.DB	SIOA_CMD		; BASE PORT (CMD PORT)
+	.DW	DEFSIOACFG		; LINE CONFIGURATION
+	.DW	SIOA_RCVBUF		; POINTER TO RCV BUFFER STRUCT
+;
+	; SIO/2 CHANNEL B
+	.DB	0			; DEVICE NUMBER (SET DURING INIT)
+	.DB	0			; SIO TYPE (SET DURING INIT)
+	.DB	1			; SIO CHANNEL (B)
+	.DB	SIOB_CMD		; BASE PORT (CMD PORT)
+	.DW	DEFSIOBCFG		; LINE CONFIGURATION
+	.DW	SIOB_RCVBUF		; POINTER TO RCV BUFFER STRUCT
+;
+SIO_CNT	.EQU	($ - SIO_CFG) / 8