7.
Frequently
Asked Questions
Does the SL485 product provide power to an attached device off the terminal block? In other words, if my RS
-485
device requires power, can it obtain that power from the SNAP Link product?
★
No. The SNAP Link family requires only a tiny fraction of the power specified by the RS
-485 standard
and does not have the capability of driving an RS
-
485 device from the SNAP Link provided power source.
If I power off and power back on a SNAP Link product, does it forget the configuration changes I have previously
applied, such as baud rate, parity, flow control, UART parameters, channel, or network ID?
★
No. SNAP Link units store those parameters into non-
volatile (NV) RAM, maintaining your settings
when power is cycled.
As shipped from the factory, are the SL485 products configured to use 2
-wire or 4-
wire RS
-
485 cabling?
★
Factory
default settings are to assume an RS
-485 2-
wire cable. To support a 4
-
wire configuration, the
unit must be opened and some settings on the six DIP switch box must be changed as shown in the
chapter on DIP switch settings.
I have a 3
-wire or 5-
wire RS
-485.
Do you support those as well?
★
Yes. Some documentation does not count the ground wire when discussing an RS
-
485 cable.
Therefore, a 2
-
wire isn’t counting the ground wire, while saying 3
-
wire does count it. They are both the
same. A 4-
wire is also the sa
me as saying 5-
wire for the same reason.
In a multipoint configuration my master device shows an amber flicker periodically. Does this mean it has a weak
signal strength? Can I determine the signal strength on the master unit?
★
No. A master’s A LED displ
ays a mostly green color, with a regular amber flash. This display simply
indicates that the unit is the master node in a multipoint network.
★
The master does not indicate signal strength when communicating with its slaves. However, by
looking at LED C you can determine when the master unit has data transmission activity with its
attached serial device.
★
The only way to determine signal strength in a multipoint network is by looking at LED A on the slave
units to see if they have a good connection with
the master.
I need to replace the master SNAP Link unit in a multipoint setup that has been working. Must I reset each device,
or can I merely set up the new master?
★
You will need to perform a simple one
-
button process at each slave. This is by design s
ince you
wouldn
’
t want slave devices to automatically switch to a new master if one were one to be powered up
for a different purpose. This is documented in the setup chapter, but the process is as follows:
1.
Hold down the MODE button for 5 seconds until LED A begins to flash red. Release the MODE button,
LED A will no longer be lit.
2.
Click the MODE button four times in rapid succession. LED A will rapidly flash amber to indicate it is
seeking a master and, upon finding one, will change to green.
Is the SNAP Link RS
-
232 product a DTE (data terminal equipment) or a DCE (data communications equipment)?
When do I need to use a null modem cable or adapter?
SNAP Link
21
Summary of Contents for SNAP Link
Page 4: ......