Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!utgpu!water!watnot!watmath!clyde!rutgers!mit-eddie!uw-beaver!tektronix!tekgen!tekigm!tekigm2!neals
From: neals@tekigm2.UUCP
Newsgroups: comp.sys.m6809
Subject: Re: CoCo3, Disto Controller, OS-9
Message-ID: <1582@tekigm2.TEK.COM>
Date: Mon, 23-Mar-87 20:51:59 EST
Article-I.D.: tekigm2.1582
Posted: Mon Mar 23 20:51:59 1987
Date-Received: Wed, 25-Mar-87 05:52:09 EST
References: <1608@lsuc.UUCP> <15129@amdcad.UUCP> <1389@loral.UUCP> <1558@tekigm2.TEK.COM> <1391@loral.UUCP>
Reply-To: neals@tekigm2.UUCP (Neal A. Sedell)
Distribution: na
Organization: Tektronix, Inc., Beaverton, OR.
Lines: 19

>>>  The single/double density select on Radio Shack and J & M disk controllers
>>>is address $FF40, bit 5 ($20): 0 = single density, 1 = double density. Other
>
>>Just thought I'd mention, before someone runs out and mod's Newdisk to clear
>>bit 5 of $FF40 to do single density, that besides being the double density
>>enable bit, it also enables the HALT circuitry.  This is because a 6809 at 
>
>  No, no, nicht, nein! The DRQ-HALT gate is $FF40, bit 7.

OK, OK, one more time.  Yes, I was wrong about the HALT enable being bit 5,
BUT bit 5 DOES enable the NMI output from the disk controller cartridge
as well as enable double density.  Therefore, if you turn off double
density there's nothing that's going to break you out of the read/write
loop.  Of course at single density speed there's enough time to poll the
status register in the loop.  Thanks for keeping me honest, Dave.

-------------------------------
 Neal Sedell     neals@tekigm2
-------------------------------