Recently, I have been developing an SBC based on the Zilog Z80 microprocessor. Since my first design, a serial connection has been essential for the board to communicate with a PC or terminal. For this purpose, I have been using Zilog's own Z80 DART (or SIO/0) because of how easy it is to interface with the Z80. However, it has been getting harder and harder to find distributors who sell these chips or similar ones, such as the 6850, for a reasonable price. Is there a newer chip or technology that I could use that would come in a DIP package and is relatively easy to interface with the Z80?

  • \$\begingroup\$ This type of question is off-topic here, but another from that era was the 8251. Don't rule out using something like a modern MCU as a supervisor providing this and other functions; for that matter consider building the whole system in an FPGA. \$\endgroup\$ – Chris Stratton Jul 23 at 1:44
  • \$\begingroup\$ @ChrisStratton thanks for the response. I'll check out the 8251. My goal here is to create a system using as many "original" chips as possible, hence why I chose the DART. I definitely don't want to make the system on an FPGA, because this project is mainly to teach myself about system architecture, but I may eventually to learn how to use an FPGA. \$\endgroup\$ – jacobtohahn Jul 23 at 1:52
  • \$\begingroup\$ The HD-6402 was a stand-alone UART. Unfortunately, Intersil apparently discontinued it in 2016. \$\endgroup\$ – Peter Bennett Jul 23 at 1:54
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    \$\begingroup\$ A desire to learn about architecture is all the more reason to use something like an FPGA; otherwise you're stuck with the limitations of available old parts, rather than being free to concentrate on sensible architecture. Anyway, part selection questions are off-topic. \$\endgroup\$ – Chris Stratton Jul 23 at 1:55
  • \$\begingroup\$ @ChrisStratton well, a lot of it stemmed from my interest in vintage computing, so I wanted to better know these computers by working with the chips they used. Another aspect was PCB design. Whatever it is, this project has taught me more about computer engineering than nearly ever other project I've done. \$\endgroup\$ – jacobtohahn Jul 23 at 3:45

Newark/Farnell have 1,931 units of NXP's SC16C550 available. Stock up now!

Other possibilities include the SC16C2552 and SC16C752.

"But they aren't DIP!" you say. Well there is simple solution for that:-

SMT Breakout PCB for 48-QFN or 48-TQFP

enter image description here

I would just use the SMD part directly though - saves board space and is easier to solder than DIP.

  • \$\begingroup\$ Thanks so much for the answer. I looked at the datasheets to all those parts and they're exactly what I need. The hardest part is gonna be choosing which one! I've never soldered SMD (other than some 0805 resistors) but I'm willing to try with some practice parts. \$\endgroup\$ – jacobtohahn Jul 23 at 3:18

Wow! I haven’t touched a Z80 since my TRS-80 in 1978!

Many PIC MCUs have very robust USARTs, along with most anything else you may want or need. They’re very affordable and if you need battery or low power, sleep currents down into the nanoamps. I’m talking $0.50 or less in volume.

Check out the 8-bit PIC12LF1822 or use the Microchip selector tool and choose device with multiple USARTS for RS-232 or RS-485. If you need something beyond old school serial, there’s I2C and more.

You can program them in C language or assembler.

And yes, they’re available in DIP packages as well as SMC.

  • \$\begingroup\$ Thanks for this. I want to try avoiding new MCUs (just to keep the originality), but on another board I may try that to also create some video generation hardware. \$\endgroup\$ – jacobtohahn Jul 23 at 3:28

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