Honeywell CIU 888 - Page 26

Electrical Installation - Field and Host Port Connections
Part No.: 4417590_Rev13 CIU 888
Installation Manual 3 - 7
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Connections over short distances can be made with a “null modem”
cable. If the distance is longer than 15 m (50 ft), a modem connection
must be used. The connection to the modem depends on the type of
modem used.
FIGURE 3-6 Field RS232C Port Connection Details
3.4.3.2 Field RS232-485 Port in RS485 mode
Refer to FIGURE 3-7 for RS-485 pin configurations and connections.
Cable requirements for RS-485 connection:
• Max. length: 1000 m (3000 ft)
• Minimum one twisted pair (typical: 50 twists per metre) with a
ground wire
• Overall shielded
• Rmax:0.12
 /m (per line)
• Cmax:119 pF/m
• Lmax:1.45 mH/m
Refer FIGURE 3-7 (A) for full duplex RS-485 connection or FIGURE 3-7
(B) when a half duplex RS-485 connection is required. For half-duplex
connect signals RXA with TXA and RXB with TXB inside the cable
connectors. Place 120
 resistors at the receive terminals in the cable
connectors.
Signal Name
Pin no.
9 Pins 25 Pins
Protective ground
DCD
RXD
TXD
DTR
Signal ground
DSR
RTS
CTS
Chassis
1
2
3
4
5
6
7
8
1
8
3
2
20
7
6
4
5
CIU 888
(female)
Prot Ground
RXD
TXD
RTS
CTS
Sign. gnd
DSR
DTR
DCD
DTE
RXD
TXD
RTS
CTS
Sign. gnd
DSR
DTR
DCD
Pin layout for 9 and 25 pins D-type connector
Null Modem Link
(female)
Prot Ground
RXD
TXD
RTS
CTS
Sign. gnd
DSR
DTR
DCD
DCE
RXD
TXD
RTS
CTS
Sign. gnd
DSR
DTR
DCD
Modem Link
CIU 888