2 Feb
2025
2 Feb
'25
6:26 p.m.
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