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Your KB—490O is aproduct of the computer age. Unlike its predecessors
the KB—42OO AND KB-4800, this unit does not use discrete dedicated parts to
perform its function. Instead, it employs an "all purpose" IC called an
integrated microprocessor. This device does nothing itself, however, when
provided with alist of instructions, it will carry them out and in so doing,
accomplish the objectives of the programmer who devised the set of instruct‘
ions. The KB—4900 uses amicroprocessor called the 5035 (developed by the
Intel Corporation). The 9035 contains an 8-bit central processor unit (CPU),
512 bits of random access memory (RAM), 27 input—output lines (1/0) and
an B~bit timer/event counter.
For instructions, we use the 2732 (Ultra-Violet) Eraseable Programmable
Read—Dn1y Memory (EPRDH). It can contain as many as 4,096 individual
instructions composed of 32,768 individual bits. The sending buffer and
message storage are implemented in another powerful IC, the 2114. This
Random—Access Memory (RAM) will store 512 Esbit bytes in its 4,096 read‘
write storage cells, and last, but not least, the venerable 9044 single
chip keyer IC provides the Morse code generation in order to free the
processor for more complicated tasks. For those of you interested in
statistics, the circuitry in the KB—4900 contains approximately
100,000 individual transistors.
The program for the KB—4900 uses most of the 4,096 instructions possible
from the 2732. From alibrary of 90 individual instructions recognized by
the microprocessor, the program is built-up into asequence that provides
the function of the KB—4900. The microprocessor winds its way through the
program at the rate of 400,000 instructions per second. And, while it looks
as though things are being done all at once, in reality they are being done
one—by—one. The processor does everything serially except that it handles
all data in groups of eight binary digits called bytes. The processor is
unbelievably busy while the unit is operation, executing the prescribed
program at the 400 KHZ rate. It is not unlike ajuggler keeping many plates
spinning at one time. Though we have only one juggler, there is awhole
lot of activity going on. In the case of the KB«4900, it may be sending DU,
accepting new key inputs, assigning spaces in the sending buffer, unloading
the sending buffer at some other point, running the buffer meter, running the
speed meter, holding the PTT line down, watching for buffer overflow, keeping
track of the time. incrementing the serial number, and scanning the keyboard
for new commands....400,000 times asecond without mistakes!
The program for the KB—4900 consists of 78 pages of single spaced text. It
took nearly six months of writing, testing and debugging to get
the program ready. we hope you enjoy using the system as much as we enjoyed
designing it, If you have suggestions on how we might improve the unit,
don’t hesitate to call or drop aline.
(D
