User`s manual

Figure 5 – Header E5, RS-485 ‘RTS’ Enabled, with ‘Echo’

Figure 6 – Header E5, RS-485 ‘DTR’ Enabled, with No Echo

Address and IRQ selection

The COML 106U is automatically assigned I/O addresses and IRQs by your motherboard BIOS. Only the I/O

address may be modified by the user.

Adding or removing other hardware may change the assignment of I/O addresses and IRQs.

Line Termination

Typically, each end of the RS-485 bus must have line-terminating resistors (RS-422 terminates at the receive end

only). A 120-ohm resistor is across each RS-422/485 data input in addition to a 1K-ohm pull-up/pull-down

combination that biases the receiver inputs. Header E4 allows customization of this interface to specific

requirements. Each jumper position corresponds to a specific portion of the interface. If multiple COML

106U adapters are configured in an RS-485 network, only the boards on each end should have jumpers T, P &

P ON. Refer to the following table for each position’s operation:

Name Function

P Adds or removes the 1K ohm pull-down resistor in the RS-422/RS-485 receiver circuit

P Adds or removes the 1K ohm pull-up resistor in the RS-422/RS-485 receiver circuit

T Adds or removes the 120 ohm termination.

L Connects the TX+ to RX+ for RS-485 two-wire operation.

L Connects the TX- to RX- for RS-485 two-wire operation.

COML 106U(-X)-D25 CyberResearch

Serial Communications