Model 100E Instruction Manual Operating Instructions
045150102 Rev XB1 95
check the cable for proper wiring. For COM2 it may be necessary to install a null-modem
cable (contact customer service for information).
6.9.4. COM2 Configuration
As delivered from the factory, COM2 is configured for RS-232 communications. This port
can be re-configured for operation as a non-isolated, half-duplex RS-485 port with a 150
Ω termination resistor (Table 6-16 shows the pin assignments of the DB-9 connector).
For RS-485 operation, jumper JP3 on the CPU board should be installed and switch 6 of
SW1 should be set to the ON position. For RS-232, remove the jumper and set the switch
to OFF (default). JP3 is just to the right of the third connector from the left on the top of
the CPU board (as seen from the inside of the analyzer). SW1 is in the middle of the CPU
board between disk-on-chip and BIOS. For non-terminated RS-485 operation, remove
the jumper on JP3 but leave switch 6 in the ON position. Refer to Figure 3-8 to locate the
CPU board.
Table 6-16: COM1 and COM2 DB-9 Pin Assignments
PIN # COM1 (RS-232) COM2 (RS-232) COM2 (RS-485)
1 Not used Not used Not used
2 TRANSMIT DATA* RECEIVE DATA DATA -
3 RECEIVE DATA* TRANSMIT DATA DATA +
4 Not used Not used Not used
5 SIGNAL GROUND SIGNAL GROUND SIGNAL GROUND
6 Not used Not used Not used
7 DATA SET READY* DATA SET READY Not used
8 REQUEST TO SEND*
(=DTE Ready)
REQUEST TO SEND
Not used
9 Not used Not used Not used
* Configurable for COM1 at rear panel using the DTE-DCE switch
6.9.5. DTE and DCE Communication
RS-232 was developed for allowing communications between data terminal equipment
(DTE) and data communication equipment (DCE). Basic terminals always fall into the DTE
category whereas modems are always considered DCE devices. The difference between
the two is the pin assignment of the Data Receive and Data Transmit functions. DTE
devices receive data on pin 2 and transmit data on pin 3, DCE devices receive data on
pin 3 and transmit data on pin 2.
To allow the analyzer to be used with terminals (DTE), modems (DCE) and computers
(which can be either), a switch mounted below the serial ports on the rear panel allows
the user to switch between the two functions.
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