Re: A89: Big Bang 89?

To: assembly-89@lists.ticalc.org
Subject: Re: A89: Big Bang 89?
From: Johan <johei804@student.liu.se>
Date: Sat, 5 Aug 2000 19:01:09 +0200
In-Reply-To: <32435408.965493956947.JavaMail.imail@bernie.excite.com>; from Jason Jackson on Sat, Aug 05, 2000
References: <32435408.965493956947.JavaMail.imail@bernie.excite.com>
Reply-To: assembly-89@lists.ticalc.org


On Sat, Aug 05, 2000 at 09:45:56AM -0700, Jason Jackson wrote:
> 
> Being a 6502 guy from way back I have a few questions. Can you bit bang the
> link port with the 68k? All we need to do is send a 8 bit, non parity, 1
> start bit 2400 baud signal out one line on the link port.
> 
> Is it possible...?   Can I please receive some information about this...?  

Basically, you can pull the line to ground or leave it floating (pull-up?).

	; enter bit bang mode (and disable link interrupts)
	move.b	#$40,$60000C

	; leave bit bang mode (reset link hardware)
	move.b	#$E0,$60000C
	move.b	#$8D,$60000C

	; pull "tip" low
	bset	#0,$60000E

	; leave "tip" floating
	bclr	#0,$60000E

	; pull "ring" low
	bset	#1,$60000E

	; leave "ring" floating
	bclr	#1,$60000E


You could probably use a timer interrupt to get ~2400 baud.
For more info on the above, see http://m101.ryd.student.liu.se/J89hw.txt


/Johan

References:

A89: Big Bang 89?

From: Jason Jackson <desolate_flux@excite.com>

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