Quatech ES-100 user manual Addressing Ports, Setting the address

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.

PORT	ADDRESS RANGE
Serial 1	Base Address + 0	to	Base Address + 7
Serial 2	Base Address + 8	to	Base Address + 15
Serial 3	Base Address + 16	to	Base Address + 23
Serial 4	Base Address + 24	to	Base Address + 31
Serial 5	Base Address + 32	to	Base Address + 39
Serial 6	Base Address + 40	to	Base Address + 47
Serial 7	Base Address + 48	to	Base Address + 55
Serial 8	Base Address + 56	to	Base Address + 63

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