Option Selection, Port Enable/Disable | Black Box IC174C, IC110C

DUAL PORT RS-232 SERIAL INTERFACE

4. Option Selection

NOTE

Be sure to set the address selections and jumper options before installation.

The board contains several jumper straps for each port which must be set for proper operation.

Port Enable/Disable

Each port on the Dual Port RS-232 can be enabled or disabled with switch position 8 on the DIP switch. The port is enabled with the switch ON (or closed) and disabled when OFF (or open). Switch 2 (SW2), position 8 enables/disables Port 1, while Switch 1 (SW1), position 8 enables/disables port 2. If either port is disabled, be sure to also disable the interrupt request for that port by removing the IRQ jumper (see Figure 4-1).

Setting the Interrupt Request

Headers E1 and E2 select the interrupt request for each serial port. If COM1: is selected, this jumper must be on the IRQ4 setting. If COM2: is selected, this jumper must be on IRQ3. Both ports can be set to the same IRQ setting. If no interrupt is desired, remove the jumper.

NOTE

Most communications software applications default COM3: to IRQ4 and

COM4: to IRQ3. This requires the sharing of interrupts between COM1:

and COM3:, and between COM2: and COM4:. While this is the default, it is not always the best setting. Check your software configuration instructions to determine the most appropriate IRQ setting.