IC for RS232

[mrtinb]

Hi
I'm trying to create a RS232 interface for my ZX81.

All schematics I've found for this:

• http://www.neoncluster.com/projects-zx8 ... aplin.html
• http://www.user.dccnet.com/wrigter/inde ... serial.htm

uses old Intel ICs: 8251 or 8255 or Z80 SIO.

They become more and more expensive because they are harder and harder to find because they are not produced anymore.
What IC can I use today for my project? (DIP please)

When I search the Internet every search result is for FTDI USB-to-RS232, but I don't need a chip for USB. I just need plain 5V UART TX,TX,RTS,CTS with configurable baud-rate.

I could also bit-bang the port in software, but I think my ZX81 has better things to do.

Edit: Added Z80 SIO

[1024MAK]

Zilog still make the SIO range (part number Z84C4x such as Z84C40). Mouser has some in stock, see here. The UK site of Farnell also lists a Z84C40. There may well be other suppliers as well.

If you want a NMOS Zilog part, I have some surplus chips, but I they are pulls from old boards and I have not tested them.

I don't know about the availability of the Intel chips, but keep in mind that there were later CMOS versions, and third party suppliers as well.

Mark

[mrtinb]

That's some of the most expensive ICs I've seen in a long while.

[mrtinb]

Ok, I found them a lot cheaper here: https://www.aliexpress.com/item/4pcs-lo ... 56575.html

[1024MAK]

Yeah, but these are brand new chips. As the market for them is rather smaller than in the 1980s, they will cost more than modern popular mass produced components.

If you want a valid comparison, on the same sites, there are new Z80 CPUs. But because more of these are sold, the price of the CPU is lower than that of the SIO chips.

If you want cheaper, try a search on eBay, or as I say, I have some NMOS SIO chips. As they are untested, I could send two for the cost of postage.

Mark

[1024MAK]

Note that there are FOUR versions of the DIL SIO, which one you use depends on which functions are brought out to the DIL pins on the package.

Read the datasheet for details

Mark

[mrtinb]

Thanks for your reply. I'll continue my project when they arrive in the mail.