Precision Digital PD941 - Manual (Page 19)

ConsoliDator Multi-Channel Controller Instruction Manual
19
Serial Communication Connections
A DB9 male connector is the port for RS-232 serial communication (using Modbus
protocol.) The ConsoliDator can be connected to Data Circuit-Terminating Equipment
(DCE) such as a radio transmitter with a regular straight-through serial cable. In cases
where connecting to Data Terminal Equipment (DTE), such as a PC, a Female-Female Null
Modem cable is necessary. Many computers are equipped with at least one 9-pin RS-232
serial port. For distances up to 50 ft, a shielded serial or null-modem cable is adequate.
More information can be found in Modbus Serial Communications (page 47)
When connecting the ConsoliDator
® to a PC via the PDA8232, it is strongly recommended
to change the ConsoliDator's parity parameter to "NONE - 8N2," for None parity, 2 stop
bits.
A null modem cable looks similar to a standard serial cable, but internally the transmit and receive lines
cross unlike in a standard serial cable and for Computer-to-ConsoliDator, both ends must be Female.
Figure 15. Serial Connections
Serial Communication Using RS-422/485
For long distances or noisy environments RS-422 and RS-485 offer superior
performance compared to RS-232. Differential signals can help nullify the effects of
ground shifts and induced noise signals that can appear as common mode voltages
on a network. RS-422 was designed for greater distances than RS-232. In its simplest
form, a pair of converters from RS-232 to RS-422 (and back again) can be used to
form an “RS-232 extension cord." Distances to 4000 ft. can be reached with RS-422.
In an application that requires more than two devices to be networked, the RS-232
data must be converted to a serial format that allows for multiple devices, such as
RS-485. For example, you can connect two or more ConsoliDators to a single
computer by converting all devices to RS-485, but only one ConsoliDator with RS-232.
Data Converters Available from Precision Digital
Serial converters available from Precision Digital support a wide range of
devices. Please reference part number PDA7485 when requesting information.
External Keypad Connections
Normally open pushbuttons may be wired to the six-terminal external keypad connector for
use when the front panel of the controller is not accessible. Keys 1 through 5 refer to the
front buttons in order from left to right.
EXT
ERNAL
KEY
P
A
D
KEY 5
KEY 4
KEY 3
KEY 2
KEY 1
COMMON