INSTALLING AND CONFIGURING THE CONTROLLER
SNAP PAC S-Series User’s Guide
18
RS-232 and RS-485 Serial Networking
SNAP PAC S-series controllers provide both RS-232 and RS-485 serial communication interfaces.
Serial communication ports and their corresponding wiring pinouts are shown on pages
53
and
55
.
RS-232 Connections
You can use the RS-232 ports on a SNAP PAC S-series controller to:
•
Direct connect to a device that supports RS-232 communication.
•
Connect to a modem and make a serial Point-to-Point Protocol (PPP) connection to a remote
PC or other device that supports PPP.
Use PAC Manager to configure the RS-232 ports for the way you want to use them (see the
instructions in the
PAC Manager User’s Guide
). Note that the controller cannot make a direct RS-232
serial connection with an Opto 22 I/O unit; however, it is possible to connect to an Opto 22 I/O unit
that supports PPP communications.
Attaching a Modem to the Controller
To work properly with the SNAP PAC S-series controller, a modem must be able to store settings in
non-volatile RAM (NVRAM) and default to those settings on reset.
IMPORTANT:
Any modem used with the controller must implement the Carrier Detect (CD) signal or use
a custom cable that connects CD to Data Terminal Ready (DTR).
1.
Connect the modem to the controller using a modem cable with female DB-9 connector. If
necessary, see
page 53
or
55
for pinout details.
2.
Store configuration settings to the modem’s NVRAM, following instructions in the user’s guide
for your modem.
NOTE: Configuration settings
must
be stored to the modem’s NVRAM so they will be loaded when the
controller sends a reset command to the modem.
3.
If PCs will dial up the controller, set up Windows dial-up networking on the PCs that will call the
controller. See the section for your operating system in
Appendix B, “B: PPP Support in
Microsoft Windows.”
4.
If you want the controller to dial up a PC, set up a remote access server (RAS) on the PC. This is
also described in
Appendix B, “B: PPP Support in Microsoft Windows.”
RS-485 Connections
You can use an RS-485 serial port on a SNAP PAC S-series controller to connect to Opto 22 I/O units
on a two-wire, RS-485 serial network. These I/O units include SNAP PAC SB-series brains, serial B3000
brains, and
mistic
remote bricks such as the G4D16R, G4D32RS, and the G4A8R. Both the PAC S1 and
PAC S2 support optional
mistic
signal interrupts. In addition, on the SNAP-PAC-S2 controller you can
use PAC Manager to configure up to four RS-485 ports either as 2-wire or 4-wire connections.
