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Switch SW1 and the first four positions of switch SW2 select
address lines A15 through A6. The fifth position of SW2 selects address
line A5 on the QS-100M and is not used on the ES-100M. This reflects the
different I/O space requirements of the two products. The remaining
address lines, A4 - A0 for the QS-100M, or A5 - A0 for the ES-100M, 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 9).
Figure 4 shows how the switches on the QS/ES-100M represent the
address values for serial ports. This figure can be used to explain the
examples shown in Figure 5.
Figure 4 --- Examination of a serial port base address
two, and one, hence the maximum value of 8+4+2+1 = 15.
A serial port's address is a 16-bit quantity that is most often expressed
in four hexadecimal (base 16) digits. A hex digit can hold a value from 0 to
15 (decimal), and is made up of four binary bits given weights of eight, four,
A possible serial port address is 5220 hex. The example below shows
how the hex digits are broken down into binary bits.
Bit weight
Binary bits
Sum of bits
Hex digits
2
2
0
5
8 4 2 1 8 4 2 1 8 4 2 1 8 4 2 1
0+4+0+1 0+0+2+0 0+0+2+0 0+0+0+0
0 1 0 1 0 0 1 0 0 0 1 0 0 0 0 0
0 1 0 1 0 0 1 0 0 0 1 0 0 0 0 0
These address bits are set by the switches.
All other bits are considered to be zero.
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Quatech QS-100M/ES-100M User's Manual