Applied Motion RS-232 - Manual (Page 245)

245 920-0002 Rev. I
2/2013
Host Command Reference
Appendix C: Host Serial Connections
Introduction
When communicating to a drive over its serial port you will always be using one of the following serial
connections: RS-232, 2-wire RS-485, or 4-wire RS-485. Out of the box we suggest starting with RS-232 along
with the programming cable and software that was supplied with your Q drive, so that you may be communicating
to and familiarizing yourself with your drive as quickly as possible. All software from Applied Motion communicate
to a drive via the supplied RS-232 programming cable. These software include:
Quick Tuner ------------------------used for tuning and configuring servo drives
Configurator------------------------used for configuring your stepper drives
Q Programmer --------------------create and edit stored Q programs, emulate a host
SCL Setup Utility -----------------basic host terminal for host emulation
If your project calls for a Q drive (or drives) running stored programs, you will use the supplied RS-232
programming cable along with Quick Tuner or Configurator and Q Programmer to setup, configure, and program
your drive(s). If your project calls for your drive(s) only running stored programs, you can read up on the RS-232
sub-section in this section and not read any more about the other serial connections. However, if your application
calls for a serial host controller (PC, PLC, HMI, or other serial device that can act as a host) being able to
communicate to the drive(s), you will need to choose one of the three available serial connections.
Available Host Serial Connections: RS-232, 2-wire RS-485, 4-wire RS-485
When choosing the best serial connection for your project, the choice may be made for you based on the
host controller you plan to use. For example, some devices only communicate via 2-wire RS-485. If you are not
restricted by your host controller, here are two guidelines for choosing the best connection.
Single or multi-axis
If your project calls for communicating to only one drive you can consider any of the three options. If your
project calls for communicating to more than one drive you should use 2-wire or 4-wire RS-485.
Long communication cables
In many applications, the limitation of 50 feet on RS-232 will be sufficient. In applications where the distance
between drive and host controller will be more than 50 feet (up to 1000 feet), you will need to choose 2-wire or
4-wire RS-485.
A Quick Summary of 2-wire and 4-wire RS-485 connections
The 2-wire and 4-wire RS-485 protocols that the drives utilize are based on industry standard RS-485 and
RS-422 protocols. Strictly defined, RS-485 is a 2-wire interface that allows multi-node connections limited to half-
duplex serial communications. Up to 32 nodes that both transmit and receive can be connected to one network.
On the other hand, RS-422 in the strictest definition is a 4-wire point-to-point connection that allows full-duplex
serial communications when connected to a single node. RS-422 has one node that is the driver or transmitter
and up to 10 nodes that are receivers. RS-422 was not designed for a true multi-node network.
2-wire interfaces require one more significant feature. A network node, master or slave, must be able to tri-
state its transmitter to allow other nodes to use the network when required. For high speed baud rates this must
be done very quickly to avoid communication collisions.
4-wire interfaces can go beyond simple point-to-point communications and be used in multi-node networks
if the slave nodes are capable of tri-stating their transmitters as required in the 2-wire networks. Some RS-485
devices (like Applied Motion drives) are set up to do this and can be used in a 4-wire, multi-node configuration.
The drives are designed to work in a multi-node environment, and so they use both the standard 2-wire
RS-485 connection, and a modified RS-422 (4-wire) connection that has been termed “4-wire RS-485”. This is
because unlike the standard RS-422, which is designed for single-node connections, the 4-wire RS-485 used by