Native Serial code on TINI

I am doing a 3rd year project where I am trying to control a Marklin train 
set. I hope to do this by using the serial port on the TINI board. I have 
had some success with using the java library to send the data to the train 
set. But I have run in to a timing issue and java doesn’t seem to give me 
enough control over the system. I need to have a break for a couple of 
hundred micro seconds which I can’t do in java. So I have started to 
research how to do it using native code.
I have written the following program to test the serial port in native mode

$include(tini.inc)
$include(ds80c390.inc)
$include(tinimacro.inc)
$include(apiequ.inc)

Serial_Init:
	clr a
	ret

Native_method1:
send:
	MOV 	sbuf1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
	CALL 	POUT
	MOV 	SBUF1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
	CALL 	POUT
	MOV 	SBUF1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
	CALL 	POUT
	MOV 	SBUF1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
	CALL 	POUT
	MOV 	SBUF1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
	CALL 	POUT
	MOV 	SBUF1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
	CALL 	POUT
	MOV 	SBUF1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
	CALL 	POUT
	MOV 	SBUF1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
	CALL 	POUT
	MOV 	SBUF1, #0ffh
	CALL 	POUT
	MOV 	SBUF1, #000h
;******** Send finished *********
	MOV	R0, #003h	;just a test value
	MOV	R1, #0h
	MOV	R2, #0h
	MOV	R3, #0h

	CLR 	A		; No errors
	RET			; Exit from Program
;************** Function for waiting between sending bytes 
******************
POUT: JNB 	TI1, POUT	; Wait here until TI bit is set
	CLR 	TI1 		; Clear TI for next byte
	RET 			; Return
END

I create a serial port object in the java code to set up the serial port. I 
then want to use the code above to send data bytes.
But at the moment the code seems to be sending random stuff. And if I try to 
run the above code more than 2 times without restarting the TINI board the 
board sends random bytes after the program has finished.

Can anyone tell me what I am doing wrong with my assembly code?

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