User manual

Communication Mode
The 422 models support Full-Duplex and Half-Duplex communications with a 4-wire cable
connection. 485 models support Half-Duplex communications with a 2-wire cable connection. Half-
Duplex allows traffic to travel in both directions, but only one way at a time. RS485 communications
commonly use the Half-Duplex mode since they share only a single pair of wires and installation cost
is reduced.
Baud Rate Ranges
The card has capability for two baud rate ranges, selectable on a port-by-port basis. One range is for
up to 115,200-baud applications and the other is for up to 460,800-baud applications. Refer to Baud
Rate Divisor Table on page 5-2 of the manual.
Auto-RTS Transceiver Control
In RS485 communications, the driver must be enabled and disabled as needed, allowing all cards to
share a 2-wire cable. The 485 cards control the individual drivers automatically. With automatic
control, the driver is enabled when data are ready to be transmitted. The driver remains enabled after
data transmission is complete for one additional character's transmission time and then is disabled.
The receiver is also normally enabled, then disabled during RS485 transmissions, and then re-
enabled after transmission is completed (plus that one character transmission time). These cards
automatically adjust their timing to the baud rate of the data. (The automatic control feature makes
the cards ideal for WIN95 applications)
Input/Output Connections
These cards use a 37-pin DBM connector and a breakout cable. The breakout cable terminates in a
DB9 connector for each port. Those DB9 connectors are equipped with 4-40 threaded standoffs
(female screw lock) to provide strain relief. The mating connector is AMP type 17D-E9s or equivalent.
We recommend using vinyl-jacketed, multiple, twisted-pair cable.
The card is also available without this cable. If your card was purchased without the cable, there will
be an "S1" appended to the model number.
To ensure that there is minimum susceptibility to EMI and minimum radiation, it is important that the
card mounting bracket be properly screwed into place and that there be a positive chassis ground.
Also, proper EMI cabling techniques (cable connect to chassis ground at the aperture, shielded
twisted-pair wiring, etc) should be used for the input/output wiring.
Manual PCI-ICM-422(485)/2(4)
6