Operating And Programming The Microkit; System Overview And Initial Operation - RCA COSMAC Operator's Manual

OPERATING AND PROGRAMMING THE MICROKIT
SYSTEM OVERVIEW AND INITIAL OPERATION
The nest for the Microkit consists of a set of printed
circuit board connectors with associated card guides
and a built-in power supply and control panel. The first
21 of the 34 available connector positions are assigned
to specific module* types. Many of their pins are pre-
wired using a printed circuit (PC) board backplane and a
small number of additional wire-wrapped connections.
(The latter were specifically made removable to permit
possible user modifications.) The last 13 of the con-
nectors are available for .any use.
Table 3 (p.44) contains a list defining to which module
each of the first 21 card positions is assigned. Eleven
of these positions are occupied with modules supplied in
the minimal Microkit, as indicated in the list. All
logic functions are implemented in COS/MOS. One card
contains the two-chip COSMAC microprocessor (the CPU --
"central processing unit"). Three memory cards are
included -- two 512-byte RAM's (random-access memories)
and one 512-byte PROM (programmable read-only memory)
containing the prewritten UTILITY PROGRAM, henceforth
called UT2. The crystal-controlled system clock and the
control-pinel interface reside on a card. Two cards are
used to provide appropriate data routing within the system.
An additional module is used for memory address latching.
Finally, three cards provide a fundamental I/O (input/out-
put) interface (including I/O device selection decoding,
a two-way byte-parallel I/O port and an I/O typewriter
serial interface). It should be emphasized that a spec-
ific, custom COSMAC controller need not require all of
these hardware facilities, if it is sufficiently simple.
Detailed descriptions of each of the available modules
appear elsewhere in this manual.
The supplied UT2 program includes a set of routines pro-
viding basic functions which virtually all users are ex-
pected to need. These include capabilities to load memory,
to read memory and to initiate program execution. Other
built-in services which are available from these routines
will be described later.
* We will use the terms "module", "card", or "board" inter-
changeably -- to represent a pluggable unit. It is in-
serted into the nest in a specified "slot" or "numbered
position". Each such slot has its own connector, mounted
in the nest.
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