Multi-Drop Programming Using Scpi Commands - TDK-Lambda GENESYS Series User Manual

12.3.3. Optional RS-485 Terminator
For very long RS-485 cable distances, or if many supplies are chained together, a
signal terminator may added to improve signal integrity. The terminator is plugged
into the J3-OUT of the last supply in the chain (see diagram above). To make a
terminator:
A. Crimp a short cable to a RJ-45 connector (or just use the end of a LAN cable)
B. Use two ¼ watt resistors, recommended value is 120 ohms, and solder them:
C. Although the RS-485 bus should not be at hazardous voltages, insulate the terminator
properly for your application

12.4. Multi-drop Programming Using SCPI Commands

12.4.1. Selecting One Power Supply in a Multi-drop Chain
All the SCPI commands in section 11 may be sent to any one of the supplies in an
RS-485 chain by first sending the INST:SEL address command. All commands and
queries will then apply only to the selected supply, until a new INST:SEL is sent
At power-up, the LAN master supply is automatically the one selected
After sending INST:SEL, it is recommended that you verify the command by sending
INST:SEL? or SYST:ERR?, otherwise the next commands could go to the wrong
supply
12.4.2. Global Commands in a Multi-drop Chain
The GLOBAL commands affect all of the chained supplies at the same time,
including the LAN supply.
There are differences between a normal SCPI command (in section 11) and a global
command. The differences are:
 There is no SYSTEM:ERROR? response message (see section 11.8.1) if one or
more supplies cannot execute a global command.
 It is required that the user's application add a 200 millisecond delay after a global
command before sending any other messages. This is because there is no
feedback from the multi-drop chain to indicate the command is still being
processed.
 There is no query version of these commands. Global settings must be queried by
selecting one power supply and reading it's setting
 The error and status registers operate differently. See section 12.4.10 for details
 The global commands are not SCPI compliant
The global commands do not affect which power supply has been selected using the
INST:SEL command. For example, if the following commands are sent:
INST:SEL 4
:VOLT 50
GLOB:VOLT 70
(wait 200 mSec)
:VOLT 90
then all the supplies on the multi-drop chain will be set to 70 volts except the supply
at RS-485 address 4 will be set to 90 volts (after the global command, another
INST:SEL was not required)
8303460000 Rev A
from pin-3 to pin-6
from pin-4 to pin-5
58
(TXD+ to TXD–)
(RXD+ to RXD–)
IA672-04-01-Rev. I