Campbell CR23X, Operator'S Manual

Page: 79 / 374

6-1
SECTION 6. 9-PIN SERIAL INPUT/OUTPUT
External communication peripherals normally connect to the CR23X through two 9-pin subminiature D-type
socket connectors located on the front panel (Figure 6.1-1). An optically isolated RS-232 port is provided for
direct connection to RS-232 devices such as a PC. Optical isolation provides immunity from ground loop
problems that can degrade single-ended measurement accuracy in systems with multiple ground
connections. The CS I/O interface utilizes (0 - 5) V signal levels and is to be used to connect to Campbell
Scientific communications peripherals. Either 9-pin interface can be used for telecommunications, however,
only one of these two interfaces can be active at once. The first 9-pin interface to receive a RING becomes
the active interface until a telecommunications sequence is terminated. When either port is active, "Busy with
COM" will show on the CR23X display. If "Busy with COM" is displayed after disconnecting the
telecommunications device, pressing any key will activate the key pad after a 2 to 3 second delay.
NOTE: Serial communications is not reliable over cable greater than 50 feet in length.
6.1 COMPUTER RS-232 9-PIN
DESCRIPTION
Direct connection of the CR23X to a PC is most
conveniently done through the "Computer
RS232" port (Figure 6.2-1). Table 6.1-1 gives a
brief description of each "Computer RS232" pin.
The Computer RS-232 port is a DCE device
when connected to a PC with a serial cable. It
also doubles as a DTE device when connected
to a modem device through a null-modem
cable.
Maximum input =
±
25V
Minimum Output =
±
5V
Typical Output =
±
7V
TABLE 6.1-1. Computer RS-232 Pin-Out
ABR = Abbreviation for the function name
PIN = Pin number
O
= Signal Out of the CR23X to a RS-232
device
I = Signal Into the CR23X from a RS-232
device
PIN ABR I/O Description
1 DTR O data terminal ready
2 TX O asynchronous transmit
3 RX I asynchronous receive
4 not used
5 GND isolated ground
6 not used
7 CTS I clear to send
8 RTS O request to send
9 RING I ring
The CR23X is supplied with a six foot 9 pin to 9
pin serial cable and a 9 to 25 pin adapter to
facilitate connection to a PC RS-232 port.
CS I/O
COMPUTER
RS232
(OPTICALLY ISOLATED)
FIGURE 6.1-1. Serial Communication
Interfaces
6.2 CS I/O 9-PIN DESCRIPTION
All Campbell Scientific communication
peripherals connect to the CR23X through the
9-pin subminiature D-type socket connector
located on the front of the Wiring Panel labeled
“CS I/O” (Figure 6.1-1). Table 6.2-1 gives a
brief description of each pin.
Pin 1
Pin 6
Pin 5
Pin 9