[torontocbm] Re: uIEC/SD comments
- From: "Brian Lyons" <brian@xxxxxxxxxxx>
- To: <torontocbm@xxxxxxxxxxxxx>
- Date: Sat, 13 Dec 2008 23:21:09 -0500
This is a very cool device with much potential.
I'm sorry I did not pick one up at WOC.
----- Original Message -----
From: Jim Brain
To: torontocbm@xxxxxxxxxxxxx
Sent: Saturday, December 13, 2008 9:42 PM
Subject: [torontocbm] Re: uIEC/SD comments
Jim Brain wrote:
I thought I'd help out with some questions here:
a.. I would not try connecting the uIEC to the serial port without power.
Without proper power, the unit essentially backfeeds and pulls power from ATN,
SRQ, DATA, CLK, and RESET through the pullup resistors on the VIC/64/128. But,
the power is very unstable, not sent to the VCC of the uC, and is not 5V. That
is why many devices appears to partially work with no power connected. If the
goal is to enable/disable, You could install a single switch on the ATN line
into the uIEC to "mute" it. But, if you bring out the "FWD/BACK" buttons from
the connector (pin 8 and 9), you can press them at the same time to silence the
device (press and hold, as I recall)
I just tested and it appears to work fine, but I would still discourage it.
Although the 1541 and other CBM drives do the same thing, they backfeed through
the 6522 VIA, which I think it better equipped to handle such things. Givne
that there are other options (and there is no reason to turn a uIEC off to save
energy, I still recommend the other options. Note that one can also put a
switch on the RESET line to prevent the device from resetting when the 64
resets (when it resets, it goes back the root directory, which may not be what
you want if you're in a D64 playing a bunch of games)
Still, it looks to handle it OK, and I could indeed by underestimating the
uC's abilities.
Jim
--
Jim Brain, Brain Innovations (X)
brain@xxxxxxxxxx
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times!
Home: http://www.jbrain.com
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