tnx.
I am (of course) not confusing parallel with serial: I just mentioned the setting on the Siglent scope in Digital Bus Menu (see screenshot) which asks for "Bit Wide".
What is one supposed to put in there?
You say 9 bit is not supported, but the fact you can define parity to Mark or Space, that is supposed to be the implementation of 9 bit decoding.
That is how the other manufacturers do and they specifically mention it for 9 bit multidrop systems with the 9th bit set to 1 when an address byte is sent.
So, are you sure the Siglent cannot handle it?
PS: the screenshot shows the TTL levels of a RS485 transceiver running @ 345600 baud where Di is the driver/sender and coming from a 80c52 processor.
Protocol= when 9th bit is set to 1, the frame is considered to be an address of a slave.
The green trace is the sending of the address byte (9 bits, 1 start and 1 stop) but doesn't get decoded correctly.
The red trace is the receiver, a slave that is answering.
As you may not be able to see; the triggering is not stable; there is a horizontal jitter all the time that impacts a correct decoding. But as said before, I can't get it right even with correct holdoff time.
If you have a suggestion to solve that, please do so.
tnx again.
Ok.
Digital probe supports 16bit wide input. In 2 groups of 8 bits.
In digital setup you can enable/disable individual bits.
You can enable only 1 bit if you want to.
You will generally enable only input bits you need.
Whatever you set in digital input settings is irrelevant to serial UART decode option.
In fact, you need to disable Digital bus display. It is not meant for this, but for decoding digital bus parallel values.
In serial UART decode options you need to set up what scope input will be source of data for RX and TX.
It can be analog or digital inputs.
Yes, unfortunately, I am sure that UART decode/trigger currently does not support addressed 9 bit mode.
As for the trigger, I can't say much with the data I have.
You cannot trigger from protocol, because 9bit is not supported.
You can use standard edge trigger with holdoff, or one of pulse triggers, with or without holdoff.
Make sure that levels for digital probe are set correctly for your signal.