NorthStar HSIO-4 User's & Technical Manual page 61

SECTION 4
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North Star HSIO-4
THEORY OF OPERATION
The HSIO-4 board consists of four independent
serial I/O ports, and some common control
logic. The major common functional blocks are
the I/O Address Decoder, the Data Buffers, the
Baud Rate Generator, and the Interrupt Header.
(See Figure 4-1.)
FUNCTIONAL BLOCK DIAGRAM OF THE HSIO-4
56
Figure 4-1
User/Technical Manual