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[questions] Re: NTP community feels broken
On 19/06/2022 01:06, chris wrote:
In practice, that will be small, since the
data sheet figures for a typical max232 assume a 2.5nf capacitive
load on the output, whereas a few inches of wire into a rs232 line
receiver setup might be much faster.
As we are talking about compliant RS232, which is the only real world
reason for not just connecting TTL directly to the RS232 port, the the
2.5nF condition is the maximum capacitance that can appear across the
driver output as the result of what it is driving. That sets a minimum
possible slew rate.
However a compliant RS232 system also has a maximum permitted slew rate,
intended to minimise cross talk, and probably also to ensure that long
cables don't ring, as the initial transient reflects backwards and
forwards. 30V/µs is the maximum permitted slew rate for a compliant
system. If your system exceeds that, even if it is using RS232 drivers,
it is not a compliant system.
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