RCA COSMAC Operator's Manual page 52

CARD NEST AND SIGNAL-NAMING CONVENTIONS (cont'd)
A note on power supply voltage notation: In the Microkit,
the power supply voltage named V DD (approximately +5V)
is the standard high signal level. This same name ('VDD')
is used to represent a different (higher) power supply
voltage level in all documentation describing the
COS~~C
chip set (e. g ., the Hicroproces s or Hanual,
COSt·~C
data
sheets, etc.).* In the Microkit, this higher level is
renamed 'CPUPWR'. We summarize this no.tational inconvenience
as follows:
CPU CHIP
DOCUMENTS
is the same power supply level as
is the same power supply level as
MICROKIT
DOCUMENTS
CPUPWR
VDD
(APPROX.
LEVEL)
+12V
+
SV
Also, note that the Microkit system (DC) GROUND, discussed
earlier, is isolated from the chassis (which is connected
to the ll5V AC power ground).
Each of the solid boxes in the Microkit Block Diagram of
Fig. 5 (p.33) corresponds to a supplied ~1icrokit module.
Both the Block Diagram and the backplane wiring schedule show
the modules generally left to right as they appear if viewed
from the backplan~ side of the kit. From the front of the
kit, memory is on the right and the I/O side of the system
is on the left. On the rear of the front panel is a pocket
with a small "PLUG IN LOCATIONS" drawing, which maps the
supplied modules into backplane slots. Unoccupied locations
have space on this drawing for the user to note modules
that are added to the system.
Some precaution should be exercised in removing and inserting
modules into the Hicrokit nest. The module cards are keyed
so that they cannot be inserted in improper positions or with
improper orientation. However, it, is possible for a key to
be pUlled out by a card removal. When removing a card,
care should be taken to exert a lateral force, without
twisting the card unnecessarily. It is also possible for
a connector contact to be dislodged as a result of improper
card removal. A short across to an adjacent contact
(1
to A,
for example) can then occur. If trouble develops after a
card removal and later reinsertion, carefully inspect the
connectors involved before attributing the problem to failed
electronics.
Special care should be taken when inserting or removing cards
from the extender card socket, since it has no key to limit
the harmful up-and-down motion.
- - - -
*
This occurs because the CPU chips allow internal
o~eration
at a higher voltage (for higher speed) than the other
logic and memory chips with which they interface.
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