Instruction Manual

9
If the host computer uses RTS and CTS or DSR and DTR, these lines should be
connected together in pairs [or as shown in the computer manual]. Normally this is done
in the RS-232 connector hood at the host computer. Alternately the effect of these lines
can be eliminated in software. The ANAFAZE 8 PID is ready to receive data; therefore
these lines are not required.
3.2.4 RS-232 NOISE PICK-UP
The RS-232 interface is designed so that all ANAFAZE 8 PID controllers on the same
RS-232 interface will be listening on initial power up. None of the units will have control
of the TXD line. A command sent through the host computer initializing the desired unit
starts proper communication between that ANAFAZE 8 PID and the host computer.
Since the TXD line is not controlled, a high impedance may result, causing some 60Hz
or 50Hz noise to be picked-up on the line. The noise may be interpreted as characters by
the host computer. This may continue until the first unit is selected. After unit selection,
the host computer should clear its input buffer. To prevent this, lower the impedance of
the TXD line by connecting a 15K ohm resistor between the host computer RXD line
and the -5 or -15 volt communication supply at the host. The reduction in the impedance
should be enough to prevent this character pick-up.
3.2.5 RS-422 OPTION
The RS-422 is similar to RS-232 with the exception that the RS-422 requires two
balanced lines for transmit and two lines for receive. The lines operate exactly out of
phase referenced to +5 and 0 volts, permitting longer interconnect lengths. ANAFAZE 8
PID connections are as follows:
PID COMPUTER
TXD +422 Output (Start bit +5 volts)
TXD* -422 Output (Start bit 0 volts)
RXD +422 Input
RXD* -422 Input
GND GND Ground
3.2.6 20ma CURRENT LOOP OPTION
Current loop is recommended for longer cable runs and noisy environments. The
ANAFAZE 8 PID current loop is optically isolated. It uses an external power supply for
the current loop which is normally included in the device communicating with the
controller. Consult ANAFAZE for recommendations.