OPTO 22 SNAP PAC S Series, Руководство пользователя

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RS-232 AND RS-485 SERIAL NETWORKING
SNAP PAC S-Series User’s Guide 18
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.
Bias and Termination
Bias : Bias the RS-485 network at one location (device) only. This is typically done at the device that is the
RS-485 master, which is normally the controller.
Termination: Configure termination at the devices that are located at both ends of the RS-485 network. For
more information, please see the appropriate data sheet or user’s guide for configuring the I/O unit or brain
that is at the end of the link.
NOTE: Bias and termination settings on S-series controllers take effect immediately.
Configuring RS-485 Connections on SNAP-PAC-S1 Controllers
RS-485 bias and termination settings are configured
using two DIP switches located on the top of the
controller.
Configuring RS-485 Connections on SNAP-PAC-S2 Controllers
The serial ports on SNAP-PAC-S2 controllers are software configurable using PAC Manager. This includes
mode, termination, and bias. For more information, see the
PAC Manager User’s Guide (form 1704). See also,
“Assigning Serial Ports on SNAP-PAC-S2 Controllers” on page 29 .
SNAP PAC S-series controller
location on RS-485 network
RS-485
termination
Termination
Active
Termination
Inactive
Switch Position Description
BIAS
ENABLE Bias: active
DISABLE Bias: inactive
TERM
ENABLE Termination: active
DISABLE Termination: inactive
DIP switches
(Portion of top view
At the End
In the Middle
(floating)