EF-Series Instruction Manual
Rev 2/01 3-5
3.3.2 EIA-485 Serial Communications Card
The EIA-485 communications cards meet EIA-485 specifications for differential, RS-485
asynchronous transmission of data over distances of up to 4000 feet. Refer to Figure 3-2. The EIA-
485 drivers are designed for true multi-point applications with multiple devices on a single bus.
This is an optional communications card for the host port. The P1 connector on the EIA-485
communication card plugs into the Main Electronics Board at P3, activating Comm1.
The interface lines of RTS are supported to control transmission. RTS must be active during TXD.
The default values for the EIA-485 communications card are: 9600 Baud Rate, 8 Data Bits, 1 Stop Bit,
No Parity, 10 millisecond Key On Delay, and 10 millisecond Key Off Delay. The maximum baud rate
is 19.2k.
The EIA-485 communications card includes LED indicators that display the status of the RXD, TXD,
and RTS control lines. LED indicators are detailed in Table 3-1.
Figure 3-2. EIA-485 Serial Communications Card
Mating Connector
LEDs
Host Terminals – Comm1
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