David Lord wrote:
Hal Murray wrote:
Some rs232 receivers I've checked datasheets for are not ttl
compatible. Different versions have different thresholds, some
versions can have threshold changed by external resistor.
If anybody finds a data sheet for a modern chip that
doesn't work right with TTL signals, please let me know
about it.
I've only mc1489 chips to play with here, on=1.25, off=1.0,
and mc1489A, on=1.95, off=0.8. Both those would be ok with
my bc337 pulldown ttl output. I'm pretty sure my old printer
required on=+3, off=-3. As for various pcs here they probably
Of course it's input current that's required which means a low
enough pullup resistor value or current drive.
David
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