;;Program      : XF_BIO.ASM
;;		 96/06/24      By Albert Chang.
;;Description  : This program does nothing but return the sended value to PC.
;;		 It shows the handshake method between C25 and PC. XF and BIO\
;;		 are used as the handshake signals. When C25 has sent the
;;		 data,it sets the XF. And when its is ready to receive data,
;;		 XF flag will be cleared. The BIO signal will tell C25 whether
;;		 PC is ready for receive or ready to send.
;;
;;			 |------|   BIO    |------|
;;			 |	|--------->|	  |
;;			 |  PC	|   XF	   | C25  |
;;			 |	|<---------|	  |
;;			 |------|	   |------|
;;
;;Note	       : 1. This program is assembled and linked under Fix-Point
;;		    Assembler and Fix-Point Linker of TI.
;;		 2. To running this file,user can use the loader and type
;;		    as following:
;;
;;		    C:\DSPC25\>load -la -r1000 xf_bio.out
;;

ibmpc	.set	0
val	.set	0

	.text
	cnfd
	ldpk	8
	rxf

poll1	bioz	next		;; PC is ready to send ?
	b	poll1

next	in	val,ibmpc	;; read a value
	sxf			;; ready to send
poll2	bioz	poll2		;; PC is ready to receive ?
	out	val,ibmpc	;; send a value
	rxf			;; ready to receive
	b	poll1

	.end