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I. INTRODUCTION
The DS-2000 is a dual channel asynchronous serial
communication adapter which utilizes balanced
differential drivers and receivers to provide RS-422-A
communications. It is capable of reliable communications
over long distances (4000 feet) within noisy industrial
environment. Data is communicated through two D-9
connectors which provide shielding from environmental
noise. Optional high speed transient suppressers may
also be installed on the DS-2000 to further reduce the
effects of environmental signal transients and surges.
The serial interface is accomplished through a pair
of 16550 Asynchronous Communication Elements (ACEs). The
16550 is compatible with the 8250 and 16450 ACEs used in
the IBM PC/XT/AT models. The 16550 also has an
additional FIFO mode that reduces CPU overhead at higher
data rates.
The DS-2000 supports sixteen base addresses for each
ACE through the Programmable Option Select (POS)
including the eight addresses designated SERIAL 1 through
SERIAL 8. The addresses are independent for each
channel. CPU interrupt level selections are also handled
through the POS. Each channel may select a separate
interrupt or share an interrupt level with other devices.
II. BOARD
DESCRIPTION
A component diagram of the DS-2000 showing the
locations of the 16550 ACEs, configuration jumpers, and
D-9 connectors is shown in figure 1. The first
communication channel is controlled by the 16550 labeled
U9, jumper J2, and is accessed through the connector
labeled CN1. The second channel uses the 16550 labeled
U10, jumper J3, and is accessed through the connector
labeled CN2. The clock rate divider for both channels is
controlled by jumper J1.
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