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Connecting to the RS-232C Port on the CPU Unit Appendix F
Recommended Wiring Methods
We recommend the following wiring methods for RS-232C, especially in environment prone to noise.
1. Use shielded twisted-pair cable for communications cables. The following RS-232C cables are
recommended.
2. Use a twisted-pair cable for each signal line and SG (signal ground) to connect the CPU Unit to a
communications partner. Also, bundle all the SG lines at the Unit and at the other device and connect
them together.
3. Connect the shield line of the communications cable to the hood (FG) of the RS-232C connector at the
Unit. Also, ground the protective earth (GR) terminal of the Power Supply Units on the CPU Rack and the
CJ-series Expansion Racks to a resistance of 100
Ω or less. The following example shows connecting
SD-SG, RD-SG, RS-SG, and CS-SG for Serial Communications Mode using a twisted-pair cable using
the peripheral bus.
Note The hood (FG) is internally connected to the protective earth (GR) terminal on the Power Supply Unit
through the CPU Rack or CJ-series Expansion Rack. FG can thus be connected by connecting the pro-
tective earth (GR) terminal on the Power Supply Unit. The hood (FG) is also electrically connected to pin
1 (FG), but the connection resistance between the shield and the FG is smaller for the hood. To reduce
contact resistance between the hood (FG) and the FG, connect the shield both to the hood (FG) and to
pin 1 (FG).
Model Manufacturer
UL2464 AWG28×5P IFS-RVV-SB (UL approved)
AWG28×5P IFVV-SB (not UL approved)
Fujikura Ltd.
UL2464-SB (MA) 5P×28AWG (7/0.127) (UL approved)
CO-MA-VV-SB 5P×28AWG (7/0.127) (not UL approved)
Hitachi Cable, Ltd.
XM2S-0911-E
Hood
Shield
SG signal line
CPU Unit
External device
Signal
name
Pin
No.
Signal
name
Actual wiring
SG signal lines
bundled together
Aluminum foil
POWER
PA205R
DC24V
AC240V
OUTPUT
RUN
INPUT
AC100-240V
L2/N
L1
GR
CONTROLLER
CJ1G-CPU44
SYSMAC
PROGRAMMABLE
ERR/ALM
RUN
COMM
INH
PRPHL
OPEN
PERIFHERAL
BUSY
MCPWR
PORT
CPU Unit
Power Supply Unit
Ground to 100 Ω
or less
Shield and GR connected
internally.
The hood will be grounded
if the GR terminal is
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