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Help with IC Pin Names

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PANewbie

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Can anyone explain the meaning of the bars sometimes ised on IC pin names? For example, Pins 3, 18, and 19 of the Harris 82C88 Bus Controller are labeled as /S1, /S2, and /S0 respectively. (The bar for /S1 was omitted on the diagram, but was used in the pin description chart.) Pin 4 of that IC is labeled as DT-/R, Pin 5 is ALE, and Pin 6 is /AEN. Pin 17 is MCE-/PDEN. (See below picture of the 82C88 pinout diagram.)

Why do some pins have bars over their names (or parts of the names), while others do not? And why are some pins labeled differently by different manufacturers of the same IC? What specifically does the bar on the pin name indicate?
 

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McGuinn

New Member
On an input, It means that the function it serves is activated when a negative going signal is received, as opposed to a postive going signal.

Example: RST (Reset) will cause a chip reset when a positive voltage is applied to the pin. /RST will cause a chip reset when a negative voltage is applied...

If it appears on an output, it means that the output is inverted i.e... Q is the inverse of /Q (NOT Q)...

Make sence?
 
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