On Sat, 1 Feb 2025, Paul Koning wrote: > I don't know if the MAX3222 is older, or just different. The RS232 > standard doesn't apply to those high rates. And I vaguely remember > seeing words that imply the line drivers should have controlled > rise/fall times. So I think the MAX3222 limits come from implementing > those rate limited edges, not from the age of the design.
Fair enough. FWIW I have a couple of configurations of these I/O port cards: dual serial, single serial/single parallel, the latter also in the ExpressCard form factor, all with the relevant D-sub connectors. They all had the 921600bps rate advertised, so clearly the line drivers used had to support it. I was quite surprised though they could go so far beyond. Sadly the PCIe UART/parallel port ASIC went out of production many years ago and it's only residual hardware that's still available to purchase brand new. It was a really good one: it went up to 15.625Mbps, with DMA support, 128-byte FIFOs, etc. Maciej
