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3. ADDRESSING PORTS
Setting the address
The base address of the ES-100D is set using the two DIP switch packs.
When setting the address selection switches, a switch in the "ON" position
specifies that the corresponding address line must be a logic 0 for the port to be
selected. Similarly, a switch in the "OFF" position forces the corresponding
address line to be a logic 1 for the port to be selected.
A full sixteen bit address decode is implemented to reduce the chance of
address conflicts with other adapters in the system. The base address of the
ES-100D can be set anywhere in the range of 0000 hex to FFFF hex. Each serial
port on the ES-100D uses 8 consecutive I/O locations. The ports reside in a
contiguous block of I/O space in eight byte increments, for a total of 64
contiguous bytes. This is shown in Figure 3.
Base Address + 56 to Base Address + 63Serial 8
Base Address + 48 to Base Address + 55Serial 7
Base Address + 40 to Base Address + 47Serial 6
Base Address + 32 to Base Address + 39Serial 5
Base Address + 24 to Base Address + 31Serial 4
Base Address + 16 to Base Address + 23Serial 3
Base Address + 8 to Base Address + 15Serial 2
Base Address + 0 to Base Address + 7Serial 1
ADDRESS RANGEPORT
Figure 3 --- Port address map
Switch SW1 and the first four positions of switch SW2 select address lines
A15 through A6. The fifth position of SW2 is not used. The remaining address
lines, A5 - A0, are used by the UART to select the register being accessed.
The sixth position on SW2 is used to enable or disable the interrupt status
register (see page 7).
Figure 4 shows how the switches on the ES-100D represent the address
values for serial ports. This figure can be used to explain the examples shown in
Figure 5.
4
Quatech ES-100D User's Manual