Apple II Super Serial Card Rebuild

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danielj
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Apple II Super Serial Card Rebuild

Post by danielj » Thu Feb 08, 2018 7:40 pm

Anyone know what X1-X6 are on this schematic segment? (Apple II Super Serial Schematic) :?
supercardwth.png
supercardwth.png (38.9 KiB) Viewed 655 times

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BigEd
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Re: Schematic notation...

Post by BigEd » Thu Feb 08, 2018 7:44 pm

I would say links you can cut (bow ties) or pad-pairs you can short (droids)

cmorley
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Re: Schematic notation...

Post by cmorley » Thu Feb 08, 2018 8:56 pm

Jumpers? Normally connected & normally open.

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vanekp
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Re: Schematic notation...

Post by vanekp » Thu Feb 08, 2018 9:07 pm

---><--- are normally connected and can be cut in the middle to break the jumper/track.
and ---ꓷD--- are open tracks where you can put a blob of solder on to make the jumper/track.
Peter.

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1024MAK
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Re: Schematic notation...

Post by 1024MAK » Thu Feb 08, 2018 9:37 pm

vanekp wrote:---><--- are normally connected and can be cut in the middle to break the jumper/track.
and ---ꓷD--- are open tracks where you can put a blob of solder on to make the jumper/track.
Peter.
What Peter said... effectively selection links.

Mark
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danielj
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Re: Schematic notation...

Post by danielj » Thu Feb 08, 2018 9:47 pm

Yup, just found a picture of the board and that tallies. Thanks all :)

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Re: Schematic notation...

Post by Prime » Fri Feb 09, 2018 1:27 am

danielj wrote:Yup, just found a picture of the board and that tallies. Thanks all :)
I have a super serial, lemme know if you want me to take some pics / make measurements etc. Wondered about doing a re-engineer of it.

Cheers.

Phill.

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danielj
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Re: Schematic notation...

Post by danielj » Fri Feb 09, 2018 7:21 am

Great minds :D - I thought it'd be a fun way of improving KiCad fu and SMT-fu. I was going to use discretes rather than cpld, keep the drivers as DIPs, and pop a normal ROM on there instead of the 2316.

d.

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Re: Schematic notation...

Post by Prime » Fri Feb 09, 2018 7:42 am

One of the things I thought of doing in a remake was a header for ttl serial, so you could plug in one of the ttl serial adapters that people use with microcontrollers. Also using one of the more modern rs232 level shifters like the max232 / max202 (or eqivilents) that just need a 5V supply.

Cheers.

Phill.

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danielj
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Re: Schematic notation...

Post by danielj » Fri Feb 09, 2018 8:01 am

Could also stick an esp8266 on it and have bbs-joy...

d.

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Re: Apple II Super Serial Card Rebuild

Post by danielj » Mon Feb 12, 2018 9:01 pm

Right, I've laid (!) out a schematic. I'd be very grateful if people could pass an eye over it and work out whether there's any big clangers on it. I apologise for the large number of labels, I wanted to get it onto one sheet but didn't want it to get too messy. It's not the neatest, but go easy! :)

On Phill's advice I've swapped the original drivers/receivers for MAX232s. This means I don't need the +12V/-12V lines so I've nixed them, but I note on the original schematic -5V had a smoothing cap on it, even though nothing used it - and on some other boards (i.e. the parallel), +12V has a smoothing cap across it even though it's not used. The question is, should I be doing this on this card?! Answers on a postcard. It passes all the ERCs as it stands, other than it wanting to know what -5V is doing as it's not driving anything.
SuperSerial.jpg

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Re: Apple II Super Serial Card Rebuild

Post by martinw » Tue Feb 13, 2018 2:58 pm

U7 Pin 25, should it be BD7 ?

Martin

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danielj
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Re: Apple II Super Serial Card Rebuild

Post by danielj » Tue Feb 13, 2018 3:21 pm

Yup! Thanks, good spot.

Shall I stick one of these and a USB port on for good measure?

http://www.ftdichip.com/Products/ICs/FT232R.htm

Still debating resistor networks or individual SMD resistors... I'll see what the sizes look like. I'm trying to keep it smaller than 100mm x 100mm (the boards will be dirt cheap if I can)

I may also use PLCC versions of the 65C51 and 27C256 too...

d.

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Re: Apple II Super Serial Card Rebuild

Post by martinw » Tue Feb 13, 2018 3:25 pm

Excellent idea, USB :)

Martin

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danielj
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Re: Apple II Super Serial Card Rebuild

Post by danielj » Tue Feb 13, 2018 3:43 pm

Does anyone know if there'll be any issue with the 65C51 outputs/inputs fanning to both the MAX232s and FTDI? Fan out/in isn't mentioned in the 65C51 datasheet. Obviously you won't use USB/RS232 at the same time. I hope. Or does it need a more elaborate switching arrangement?

d.

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hoglet
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Re: Apple II Super Serial Card Rebuild

Post by hoglet » Tue Feb 13, 2018 7:53 pm

What make of 65C51 are you planning to use?

As far as I understand, the most widely available one today, the WD65C51, has a serious bug with the transmit status flags rendering almost useless:
Transmitter Data Register Empty (Bit 4)

The Transmitter Data Register Empty (TDRE) bit is always a 1 because the TSR is loaded when the TDR is written to. TDRE bit cannot be polled to determine when to write the next byte to the TDR/TSR. A delay loop should be used to gate the writing to the TDR/TSR. Transmitter Interrupts should never be enabled.
See this thread for more details:
http://forum.6502.org/viewtopic.php?f=4&t=4587

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danielj
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Re: Apple II Super Serial Card Rebuild

Post by danielj » Tue Feb 13, 2018 9:50 pm

Yes, I'd just spotted that a bit earlier :( The WDCs are the most available, but they would appear to be out of the running. Rockwells seem to be the best bet. If it's to remain compatible with old software I'm guessing it really needs a 6551 in it.

It's just a question of identifying a reliable source, which *isn't* re-worked WDCs :D

d.

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Re: Apple II Super Serial Card Rebuild

Post by Prime » Tue Feb 13, 2018 11:45 pm

danielj wrote:Does anyone know if there'll be any issue with the 65C51 outputs/inputs fanning to both the MAX232s and FTDI? Fan out/in isn't mentioned in the 65C51 datasheet. Obviously you won't use USB/RS232 at the same time. I hope. Or does it need a more elaborate switching arrangement?
For outputs from the 6551, I suspect that driving both the MAX232 and the FTDI at the same time would not be a problem, however tying the inputs from the MAX and FTDI could well be a problem if one happens to pull up and the other down. Would suggest a jumper bank or some additional logic.

If you are also going to go for surface mount components, please please use something that you don't need bionic eyes so solder.

Cheers.

Phill.

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danielj
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Re: Apple II Super Serial Card Rebuild

Post by danielj » Wed Feb 14, 2018 6:04 am

Not 0405s then? :D
Fear not, sticking with 0805s and soics. I just want to keep it to under 10cm square if I can.

I might leave the FTDI out as it can easily be plugged in externally solving the issue immediately :) from a design point of view it makes more sense to have it in the cable.

d.

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Re: Apple II Super Serial Card Rebuild

Post by Prime » Wed Feb 14, 2018 7:41 am

danielj wrote: I might leave the FTDI out as it can easily be plugged in externally solving the issue immediately :) from a design point of view it makes more sense to have it in the cable.
Except then you are converting 5v->+/-12V and then back again. Guess if you used a group of 7 jumpers (pin type), so disconnect jumpers them and plug in 5v ftdi chip. Or connect them for traditional rs232.

Cheers.

Phill.

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