IBM Series 1 User Manual page 221

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This subsection will highlight some aspects of device
adapter design that are considered to be deserving of
further explanation. In some cases, typical circuits are
used as a vehicle to explain the aspect under discussion.
The area of logic represented should not be taken in the
context of a total design, when other considerations would
result in added function to a logic area. For example, the
figures assume one device only, although an attachment may
service more than one device. The logic figures use the
following conventions:
• Connections--Those with a circled "I" indicate a unit
load or drive to the device interface with the channel;
those with a circled
"J"
indicate a jumper connection.
Circled dots indicate that the signa~ is connected to
another figure in this subsection. Dots alone indicate
that the signal would be used or originates elsewhere
in an attachment, but is not connected to another
figure.
•
Logic--Wedges indicate negative active signals. Logic
blocks
are
labeled with a
particular
logic function;
the blocks perform that particular logic function with
the polarity of the inputs as shown for the block.
Except for the invert function, logic functions are
considered to produce
d
positive output internal to a
block. In some cases, a
logic function is combined
with a signal inversion to indicate the complete
function of the block.
• Labels--Signal lines are labeled with the polarity
appropriate to the active level of the signal.
2-44 GA34-00)3
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