This is the simplified block diagram of a MAX3243 line driver.
The DIN-->(inverter)-->DOUT , does it mean that if we supply DIN with 3V, then DOUT(Rs232) will be -3V ?

Thanks!

 

Yes. RS232 is inverted. Mark is <-3V, Space is >+3V

 

Yes. RS232 is inverted. Mark is <-3V, Space is >+3V

Thanks Ian, follow up question as i am still confused with this circuit. are you familiar with this?
the out* is going to a serial port connector and Dout is from a Max3243.

 

Thanks Ian, follow up question as i am still confused with this circuit. are you familiar with this?
the out* is going to a serial port connector and Dout is from a Max3243.
View attachment 357754

Looks dubious. That red NPN transistor isn’t going to enjoy the negative going output from the MAX3243.

 

Looks dubious. That red NPN transistor isn’t going to enjoy the negative going output from the MAX3243.

sorry, wrong connection. this is the right one, but its still confusing. Does it look good to you?

 

From the data sheet.

 

Thanks Ron, i actually saw this but just want to make sure because i am analyzing a circuit involving max3243 that doesnt make sense to me. But im not really good at this.

 

Thanks Ron, i actually saw this but just want to make sure because i am analyzing a circuit involving max3243 that doesnt make sense to me. But im not really good at this.

What is it supposed to do? One would expect the MAX3243 to be connected to the TXD and RXD pins of a microcontroller, rather than a bunch of transistors.

 

the input at the left side (where i put +3.3V) is an RTS TTL output from a cp2105. i simulated the circuit and the output goes 12V when input is 0 and -3.3V when the input is high(3.3V). Also the output serves as a power to a serial port connector.

Every serial port in this board has this circuit and I don't know what is this for,

 

the input at the left side (where i put +3.3V) is an RTS TTL output from a cp2105. i simulated the circuit and the output goes 12V when input is 0 and -3.3V when the input is high(3.3V).

Just to be clear, this bunch of discrete parts is on the RTS output of more than one CP2105?

Also the output serves as a power to a serial port connector.

Can you expand on that; what do you mean? What pin on the serial port (assuming a DB9 or DB25 connector).

Every serial port in this board has this circuit and I don't know what is this for,

My guess is that is some form of low speed 1-wire signalling where power and data are distributed on a single wire (ignoring the ground return of course) for a low-power peripheral.

 

1. Just to be clear, this bunch of discrete parts is on the RTS output of more than one CP2105?
2. Can you expand on that; what do you mean? What pin on the serial port (assuming a DB9 or DB25 connector).
3. My guess is that is some form of low speed 1-wire signalling where power and data are distributed on a single wire (ignoring the ground return of course) for a low-power peripheral.

1. there are multiple cp2105 and each of the RTS output have that circuit.
2. its an RJ connector , maybe for a custom peripheral but i think that the output of the discrete parts (at the mosfet drain) will power that peripheral.
3. thanks for the inputs, it can be that also.

The reason i am asking is because i thought this is a common/standard/usual circuit but seems like its not. Maybe it will be difficult to analyze if we don't know what peripheral is this used for.


Thanks again guys for the inputs. I'll move on from this.