diff --git a/libsrc/atari/siocall.s b/libsrc/atari/siocall.s
new file mode 100644
index 000000000..db71e44ec
--- /dev/null
+++ b/libsrc/atari/siocall.s
@@ -0,0 +1,60 @@
+;
+; Christian Groessler, October 2000
+;
+; this file provides the __sio_call function
+; the function does a SIO call, it's not completely
+; generic (e.g. transfer size is fixed), it's used
+; to save space with _dio_read and _dio_write functions
+;
+; unsigned char __fastcall__ _sio_call(_driveid_t drive_id,
+;				       _sectnum_t sect_num,
+;				       void *buffer,
+;				       unsigned int sio_val);
+; _driveid_t - 8bit
+; _sectnum_t - 16bit
+; sio_cal is (sio_command | sio_direction << 8)
+;
+
+	.export		__sio_call
+	.include	"atari.inc"
+	.import		popa,popax
+
+.proc	__sio_call
+
+	sta	DCOMND		; set command into DCB
+	stx	DSTATS		; set data flow directon
+	jsr	popax		; get buffer address
+	sta	DBUFLO		; set buffer address into DCB
+	stx	DBUFHI
+	jsr	popax
+	sta	DAUX1		; set sector #
+	stx	DAUX2
+	jsr	popa
+	cmp	#16
+	bcs	_inv_dev	; invalid device #
+	adc	#1
+	sta	DUNIT		; unit number (d1,d2,d3,...)
+	lda	#$31		; D1 (drive_id == 0) has id $31
+	sta	DDEVIC
+	lda	#0
+	sta	DBYTHI		; high byte of bytes to transfer
+	lda	#15
+	sta	DTIMLO		; value got from DOS source
+	lda	#128
+	sta	DBYTLO		; low byte of bytes to transfer	
+
+	jsr	SIOV		; execute
+
+	ldx	#0
+	lda	DSTATS
+	bmi	_req_err	; error occurred
+	txa			; no error occurred
+_req_err:
+	rts
+
+_inv_dev:
+	ldx	#0
+	lda	#NONDEV		; non-existent device error
+	rts
+
+.endproc