Multiple Daugherboards on one Smart Serial Port?

Everywhere in the docs it is described that it is possible to connect up to 8 remote serial daughter cards to one smart serial port.
But how? There is no jumper on those boards to select the address.
Maybe the parameter NVUNITNUMBER (Non-volatile unit number) or UNITNUMBER (Working unit number) has to be set?
And how to connect the devices? Daisy chaining?

You can only have one remote device per serial channel.

A port is a sserial host controller which may have from 1 to 8 channels
Up to 4 sserial ports may be present in a single configuration

PCW wrote:

You can only have one remote device per serial channel.

A port is a sserial host controller which may have from 1 to 8 channels
Up to 4 sserial ports may be present in a single configuration

So a channel corresponds to a physical RS-422 connection?
And a port corresponds to a driver instance or in other words to a mesa card?

A 7i74 gives you 8 smart serial ports

mesaus.com/product/7i74/

JT

JT wrote:

A 7i74 gives you 8 smart serial ports

mesaus.com/product/7i74/

JT

According to my understanding this gives me 8 Smart Serial channels. So I can connect up to 8 daughter boards.

 

HansU wrote:

PCW wrote:

You can only have one remote device per serial channel.

A port is a sserial host controller which may have from 1 to 8 channels
Up to 4 sserial ports may be present in a single configuration

So a channel corresponds to a physical RS-422 connection?
And a port corresponds to a driver instance or in other words to a mesa card?
 

A port corresponds to a controller instance in a FPGA card
There can be up to four controller instances in one FPGA card.
Each port can have 1..8 channels.

HAL Identifiers include the port and channel number, for example:

hm2_7i96s.0.7i87.P.C.analogin1

Where P is the port number and C is the channel number.

I think what is really confusing us is the fact that each channel are RS422/485, which is known to be multi-drop, thus allowing to connect multiple devices to a single communication channel (by definition). Now, PCW specifically mentioned that "You can only have one remote device per serial channel" for the mesa card, thus allowing only ONE connection per channel.

I would be tempted to now ask why, although I would guess it is some hardware limitation since the 'ports' are emulated in the case of the mesa card and are not 'real' hardware ports.

Ok now I got it. Thanks for clarifying. Maybe I should make the documentation more specific at this point.

The reasons for using one device per port are speed and timing related
and the better electrical specifications of full duplex RS-422 links
vs RS-485 links.

(because there is no undriven state that requires micky-mouse termination schemes)