IBM Series 1 User Manual page 59

Desig,!! ConsideratiQ!!2
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Operationa.l
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This subsection viII 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.l 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 a positive output internal to a
block. In S08e 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.
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