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_________________________________________________________________ 27
Hardware Structure
of the CDS
This section of the manual is organized to a present
a "top down" explanation of the hardware structure
of the COSMAC Development System. First, an
over-all system block diagram is given containing
sufficient detail to explain the basic functions of each
of the modules and to indicate all of the essential data
and control paths in the system. -A few "second-
order" signals are omitted at this stage for simplicity.
This overall diagram is followed by a block diagram
of each of the modules. These diagrams are designed
to provide sufficient detail (signal mnemonics, timing
information, etc.
I
so that further user analysis of the
individual module logic diagrams (given in Appendix
D) should be unnecessary. The assignment of con-
nector pins to signals is omitted at this point. This
detail is found in the backplane wiring schedule in
AppendixA.
A fundamental prerequisite to understanding the
structure of the CDS is a detailed familiarity with the
COSMAC CPU interface and instruction set, as
described in the User Manual for the RCA CD-
Pl802 COSMAC Microprocessor, MPM-201.
System
Block Diagram
The broad organization of the Development
System is indicated in Fig. 6. The CPU module in-
terfaces with an I/O system to its right in the diagram
and with a memory system to its left. The switches
and indicators on the Control Panel (at the top of the
diagraml communicate with the system through the
CLOCK and CONTROL Module, which also
eontains the system clock.
Most of the signal paths in the diagram are labeled
with signal mnemonics in parentheses. The notation
I i:j I is used to denote a parallel set of signals, each
labeled with a unique index in the range ito j. Thus,
for example, A(l4: 121 represents the bundle of three
parallel signals A14, A13 and A12. Note further that
where additional emphasis is required to distinguish it
from the letter "0", a
"~"
is used for the numeral
zero.
The superscript after each module name in the
diagram denotes the plug-in connector position or slot
number in the CDS next to which the module is
assigned.
Physically, the Development System consists of a
card nest with 25 sockets for logic cards in-
terconnected by means of a printed circuit backplane,
a power supply, a chassis which will mount via a 19"
rack or a cabinet, and a hinged panel on which are
mounted control switches and indicators.
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