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ADDRESSING
VI. ADDRESSING
Each channel of the DS-2000 uses 8 consecutive I/O
address locations. The base addresses are independent
but must begin on an even 8-byte boundary (xxx0H - xxx7H
or xxx8H - xxxFH). The numbers xxx are controlled by the
Programmable Option Select (POS) and address decoders to
provide complete 16-bit addressing for each channel.
Sixteen choices of base address are provided for each
channel and include the eight addresses defined as SERIAL
1 through SERIAL 8. The remaining eight addresses are a
constant 8000H offset from these values. A complete
table of available addresses is given in figure 17. The
16550 utilizes its eight assigned addresses as shown in
figure 2.
VII. INTERRUPTS
The DS-2000 is capable of supporting four interrupt
levels, IRQ 3,4,7 and 9. Each channel may select a
separate interrupt or one may be shared by both channels.
If interrupt sharing is used, the interrupt pending (IP)
bit in the interrupt identification register should be
used to test for the source of the interrupt.
CAUTION:
To maintain compatibility with earlier personal
computer systems, the user defined output, OUT 2, is
used as an external interrupt enable and must be set
active for interrupts to be acknowledged. OUT 2 is
accessed through the 16550's MODEM control register.
VIII. PROGRAMMABLE
OPTION SELECT
The IBM PS/2 family of computers using the
MicroChannel bus structure utilize on board registers
referred to as the Programmable Option Select (POS)
registers to hold the adapter's configuration
information. The first two POS registers hold a unique
adapter identification number that has been issued to Qua
Tech for the DS-2000. This number is defined in hardware
and can not be changed. These registers are read only.
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