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[fsafstrom]

If you feel like making a simple 19200 Baud comm port, here is one suggestion.

All you need is,
One 6551 ACIA.
One MAX 232 level converter.
Four 1uF electrolytic capacitors.
One Oscillator 1.8432 MHz.
One 9 pin D-SUB female.
One protoboard.
One 40 pin IDE cable.
Some wires for connection.

Optional,
MAX 702 Reset circuit.





All +5V and GND was connected on the bottom side...

[kgreene]

Cool, do you have a schematic?

[fsafstrom]

I don't really have a schematic.

Most is explained in this thread though,
http://www.brielcomputers.com/phpBB2/viewtopic.php?t=190

Let me make a description on how to hook it up tonight...
Kind of step by step instructions...

/Bamse

[fsafstrom]

Step by Step, part one...

The protoboard I'm using has 25 rows and is very similar to this one from Radio Schack.
http://www.radioshack.com/product/index.jsp?productId=2102845&cp=&sr=1&origkw=boards&kw=boards&parentPage=search

I suggest using sockets for the chips if you have any.

Start by soldering down the socket for the 6551, or if you have no socket, the 6551 itself.

This one should have one free row on it's left side, the first pin (look for the notch or dot) should face this row.
It should also be a little bit off center, see the two center columns that connects row 1-25.
The pins 1-14 on the socket or 6551 should be in the next row over from the middle columns.
See the picture from the bottom.

OK, now for the IDE cable.
Wire number one is the wire closes to the crystal and reset button on your Replica.

Connect like this,

[Mojoseph_12]

can you finish your steps
please!

[fsafstrom]

Here we go...

Now that you have all the wires we need from the cable, let's finish the 6551 part and make sure it works.

On the proto board side, connect row 25 (RES) to pin 4 (RES) on the 6551.
Then connect row 9 ($C000-CFFF) to pin 3 (CS1) on the 6551.
Connect row 10 (A0) to pin 13 (RS0) on the 6551.
Connect row 11 (A1) to pin 14 (RS1) on the 6551.
Make a solder bridge under the board between pin 16 (DSR) and 17 (DSR) on the 6551.

Solder your Oscillator so that pin 8 (output) on the oscillator is connected to pin 6 (XTAL1) on the 6551.

If you are using the MAX702 solder it down next to the Oscillator, just leave a couple of rows in between.

Get some very fine cable (I used AWG30), turn the board up side down and connect 5V and GND.

Connect pin 17 (DSR) to pin 1 (GND) on the 6551.
Connect pin 15 (Vcc) to pin 2 (CS0) on the 6551.
Connect pin 1 (GND) on the 6551 to pin 7 (GND) on the Oscillator.
Connect pin 2 (CS0) on the 6551 to pin 14 (5V) on the Oscillator.

If you are using the MAX 702,
Connect pin 7 (GND) on the Oscillator to pin 3 (GND) on the Max702.
Connect pin 14 (5V) on the Oscillator to pin 2 (Vcc) on the Max702.
Connect pin 4 (RES) on the 6551 to pin 7 (RES) on the Max702.

Double check all connections...

If you have a Multi Meter, check that there is not a short between 5V and GND.
For example, there should not be a short between pin 7 and 14 on the Oscillator. There might be some resistant due to the Oscillator it self, but it should not be a short...

Hook it up to your Replica.
Turn on and be careful, if the led does not come on, turn off, unhook and double check it again.

Once everything looks normal, type the following in Woz Mon,
C000.C003
Woz Mon should reply something like,
C000: 0D 10 0B 1F
If it replied,
C000: C0 C0 C0 C0
Something is wrong...

Type,
C002: 0B 1F
Then,
C002.C003
Woz Mon should reply,
C002: 0B 1F

If it does, that means the 6551 part is OK...

Later on, the Max232 part and the connection cable...

[Mojoseph_12]

Can the acia (6551) be addressed to A000.AFFF or B000.BFFF instead of C000.CFFF

[Kallikak]

$A000 and $B000 (pins 13 and 32 respectively - using Vince's numbering) are both available on the expansion interface, so I presume it's simply a matter of changing that one connection (and of course any associated code). You could also add a little bit of logic to make it work from $8000 or $9000 without much trouble.

[fsafstrom]

Just as Ken said, use $A000-AFFF or $B000-BFFF to change the mapping for the 6551.

On the IDE cable, $A000-AFFF is wire number 25 and $B000-BFFF is wire 24.

Another note,
Without any address logic, this is really going to use up $C000-CFFF.
Since only A0 and A1 is used, the 6551 is mapped every 4 bytes.

For example,
C000.C00F
C000: 0D 10 0B 1F 0D 10 0B 1F
C008: 0D 10 0B 1F 0D 10 0B 1F
And so on all the way to $CFFF...

Same would go for $A000 or $B000...

/Bamse

[fsafstrom]

And now the Level shifter MAX 232...

Start by soldering it down next to the 6551, take a close look at the picture to get everything correct.
Next the capacitors.
C1 goes between pin 1 and 3, negative (the marked side) is connected to 3.
C2 goes to pin 2 and to an open space on the breadboard, negative is on the breadboard.
C3 goes between pin 4 and 5, negative (the marked side) is connected to 5.
C4 goes to pin 6 and to an open space on the breadboard, negative is connected to 6.
Remember all those +5V and GND we connected on the underside ?
Well, we need to connect the MAX232 and the two capacitors that are soldered on the breadboard.
On the under side, connect pin 15 on the MAX 232 to GND, for example pin 3 on the MAX702 and then also connect C4 to GND.
Connect pin 16 to +5V, for example pin 2 on the MAX702 and then also connect C2 to +5V.
Note that you connect the capacitors C2 and C4 to the reverse polarity so to say, this id by design...

Now, the 6551 to the MAX232...
Connect pin 10 on the 6551 to pin 11 on the Max232.
Connect pin 12 on the 6551 to pin 12 on the Max232.
Connect pin 9 on the 6551 to pin 9 on the Max232.
Connect pin 8 on the 6551 to pin 10 on the Max232.

And finally the 9 pin Female D-sub...
Connect pin 14 on the Max232 to pin 2 on the D-sub.
Connect pin 13 on the Max232 to pin 3 on the D-sub.
Connect pin 8 on the Max232 to pin 7 on the D-sub.
Connect pin 7 on the Max232 to pin 8 on the D-sub.
Connect pin 15 on the Max232 to pin 5 on the D-sub.
On the D-sub, also connect pin 4 to 6 inside the D-sub.

Hook it up to your Replica, download the EWoz Mon and enjoy 19200 Baud...

That's it folks...

[vbriel]

I think people would like to see a visable schematic so I'll see if I can draw one up and post it online.

Vince

[fsafstrom]

Thanks Vince...

My Eagle Layout Editor skills are non-existent...
I tend to work on the breadboard and with the chips datasheet...

/Bamse

[Mojoseph_12]

Did you ever have a problem with writing to the command and control register for example i would write A001:70 then i would get A002: F0. If i wrote somthing above 80 @$A002 or $A003 i would get the same data back but 70 or below does not work. Did some thing like this ever happen to you.If not what would you suggest would be the problem?

[fsafstrom]

Howdy...

This sounds very familiar and my guess would be that writing to $A001 is the same as a software reset...
However, as long as don't write to $A001, I can read and write from $A002 and $A003 just fine.

Most of my stuff are still in boxes, we just got a new house and I just have not had the time to unpack.

Please try to write $0B to $A002 and $1F to $A003, this should set the baud to 19200, 8 data bits, No parity, 1 stop bit and no flow control.
Then read and write to $A000 to send and receive.
$A001 is the status register and should only be read from...

[Mojoseph_12]

The bus strip I was using was defected, D7 was not connected so the D7 floated on the 6551 giving me false readings.