1 Feb
2025
1 Feb
'25
7:03 p.m.
On Jan 31, 2025, at 10:37 PM, Maciej W. Rozycki
<macro(a)orcam.me.uk> wrote:
Sure does.
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.
paul
...
The serial port hardware I refer to uses a UART wired to a Zywyn ZT3243F
line driver, which according to the manufacturer's datasheet signals at
±5V minimum transmitter voltage levels and accepts up to ±25V receiver
voltage levels and: "Meets or Exceeds the EIA/TIA-232F and CCITT V.28/V.24
Specifications for VCC at +3.3V ±10% and +5V ±10% Operations." While the
transmitter voltage levels are not the highest recognised by the standard
I do believe this line driver does comply with RS-232.
As I say the datasheet explicitly says: "Guaranteed data rate 1000kbps,"
and according to my findings quoted above it is indeed the case (and well
beyond). [Yes, I got it wrong by writing 1MHz rather than 1Mbps, a mental
slip I suppose.]
NB I've also used the TI TRS3122E line driver, suitable for operation
with 1.8V signalling per my requirement, and it is also documented to
handle "data rates up to 1000kbps, while maintaining RS-232-compatible
output levels." I haven't got a chance to go beyond 230400bps with this
device though, but these two samples do suggest that supported operation
at 1Mbps isn't that uncommon for currently available RS-232 line drivers.
I've looked up the MAX3222 datasheet and it does say 250kbps max though;
I guess it's older technology then?
Does this answer your question?