DUAL PORT
3. Address Selection
NOTE
Be sure to set the address selections and jumper options before installation.
Each serial port on the Dual Port
8 consecutive I/O locations. DIP switch SW1 sets the base address for Port 1, and DIP switch SW2 sets the address for Port 2. Be careful when selecting the base address, since some selections conflict with existing PC ports. The following table shows several examples that usually do not cause a conflict.
Address |
| Binary |
|
| Switch Position Setting |
|
| |||
Hex | A9 | A0 | 1 | 2 |
| 3 | 4 | 5 | 6 | 7 |
1010000XXX | OFF | ON |
| OFF | ON | ON | ON | ON | ||
1010100XXX | OFF | ON |
| OFF | ON | OFF | ON | ON | ||
1011101XXX | OFF | ON |
| OFF | OFF | OFF | ON | OFF | ||
1011111XXX | OFF | ON |
| OFF | OFF | OFF | OFF | OFF | ||
1111101XXX | OFF | OFF |
| OFF | OFF | OFF | ON | OFF | ||
1100000XXX | OFF | OFF |
| ON | ON | ON | ON | ON | ||
1100101XXX | OFF | OFF |
| ON | ON | OFF | ON | OFF | ||
1111111XXX | OFF | OFF |
| OFF | OFF | OFF | OFF | OFF | ||
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Typically COM1:=3F8h; COM2:=2F8h; COM3:=3E8h; COM4:=2E8h
The following illustration shows the correlation between the DIP switch setting and the address bits used to determine the base address. In the figure below, the address 300 hex through 307 hex is selected (300 hex =11 0000 0XXX in binary representation). Note that setting the switch ON (or closed) corresponds to a “0” in the address, while leaving it OFF (or open) corresponds to a “1.”
A9 | A3 EN |
0
1
ON
OFF
1 2 3 4 5 6 7 8
6