I need 2 or 3 65c51 chips to play with.
I'm building a wiport into a c128 computer, but I'm having trouble locating any 65c51 chips except ebay.
I'm located in the US.

Any suggestions?


Thanks,
Later,
dabone

if you can't find any, you might try an Exar USART.

They have a 68xx-compatible bus.

The XR68C92 is a 40 pin DIP with 2 USARTS on board.
Here's the datasheet:
http://www.exar.com/Files/Documents/xr6 ... 080505.pdf

I used their tiny XR16L580 with my 65816 and it worked well.

Daryl

WDC makes it in 14MHz+. It's on their website here. I know their early production ones had some kind of little bug. Does anyone know if they've gotten the bug out?

Last time I checked, still only engineering samples. not for sale yet.

Daryl

Frankly, I think the programming interface of the 6551 is horridly broken.
At least of the original one. The signal lines do not work independently of the transmitter or receiver. So for example if you stop the remote side from sending in an inappropriate moment, you chop off the last bits from the byte you're currently receiving. I always had to implemented RTS/CTS independently of the 6551. Maybe it's me, but I really don't like that chip.

In my designs I use the 16550 or derivatives. It comes from the intel world, so some (small) glue logic is needed, but it even comes with a FIFO - which helps (me) a lot with higher speeds.

Well I'm using the 6551 because it's going into a commodore and the designs and software are already there.
I'm just using it to hook up more modern terminal servers like the wiport and digi connect me.

Anyway I found some 6551a's.

Thanks anyway.


Later,
dabone

I seem to remember that they weren't all the same in that regard. I never really used the NMOS ones, but I didn't have that trouble with the Rockwell and CMD CMOS ones. There are indeed things that are awkward, but I was always able to set the RTS output (CTS input to the other end) false asynchronously with no loss of data.

For future projects I think I'll just use the 14-pin-DIP MAX3100 with SPI and its 8-byte FIFOs. It doesn't have the full complement of signals for a modem, but that's hardly an issue anymore, and they could be implemented with other I/O bits if you really had to have them.

NICE. I've been a MAX232 fan but how steep is the learning curve to use the 3100 instead? It would be something I would add to the SBC 1 type deal without going all around crazed...

_________________
"My biggest dream in life? Building black plywood Habitrails"

Somehow I missed this one back when you posted it Tony, and wouldn't have seen it if heaths hadn't posted today. The MAX232 is just a pair of 5V-only line drivers and receivers (using internal charge pumps to get the required high voltages), whereas the MAX3100 is a UART. The MAX3110 is the UART plus the line drivers and receivers. The 3100 is also IrDA-compatible (for infrared links).

These UARTs have their connection to the processor through SPI instead of being directly on the processor's data bus. This has advantages and disadvantages as I'm sure you're familiar with by now; but the 3100, aside from lacking DSR, DTR, and RI I/O for modems (which could be substituted with 6522 VIA pins anyway if really necessary), is generally more capable than the 6551. It does of course have RTS and CTS. Since the commands and registers and other things are different, you will indeed have to learn a new part. It is definitely nowhere near a drop-in replacement even in programming let alone hardware; but it's not difficult at all. I just went by the data sheet for the SPI signals which I got through a 65c22, wrote my test code in Forth, and it worked without problems the first time I tried it.

I'd avoid the 6551 if possible. It's a lame design and has a nasty programming model, as Andre noted. Take a look at the 2692 DUART for a much more flexible design. You have to do more to interface it to a 65xx style bus, but I think the effort is worth it. It also can support speeds to 115.2 Kbps, has built-in timers and all sorts of cool toys to play with.

See http://www.semiconductors.com/acrobat/d ... 2692_3.pdf for a datasheet. Also look at http://www.mouser.com/Search/ProductDet ... 2692AC1N40 for a source.