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RS-232 OPERATING INSTRUCTIONS
GENERAL
This chapter summarizes operation of the MASS FLOW
COMPUTER (922-MFC) with a remote terminal.
recommended that you read the preceding chapters of the
Operating Instructions. You should be familiar with the
format and methods used in setting up the basic instru-
ment before using the RS-232 communication option.
Setting up the RS-232 Link
The RS-232 connector is a standard 25 pin female connec-
tor (DB25S), and it is located at the rear of the instru-
ment. Figure 8-1 shows a wiring diagram for the Sub-D 25
Pin connector. Standard inputs must present a load of
3000 to 7000 Ohms. A voltage level of +3V to +25V
(reference to signal ground) is read as a "Space" or "0"
and indicates an active state (asserts a control line). A
voltage level of -3V to -25V is read as a "Mark" or "1" and
does not indicate an active state (does not assert a control
line). Outputs must send a voltage of +5V to +25V (refer-
ence to signal ground) for a "Space" and a voltage of -5V to
-25V for a "Mark" when loaded with a 3000 Ohm load to
signal ground. Outputs must be capable of being shorted
to other signal lines without burning out. It is normally
recommended that cable length be limited to 50 feet.
Ground (7)
Printer Busy (11)
Pins 6, 8 and 20 are internally jumpered together
Pins 4 and 5 are internally jumpered together
13 12
11 10
9
8
25 24 23 22 21
Figure 8-1
7
6
5
4
3
20 19 18
17 16 15
8-2
Transmit (3)
Receive (2)
2
1
DB25S
14
It is
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