This Serial Communications Controller from Zilog lists a few of its pins with a bar above the name. What does this bar mean?
From a schematic I have been looking it seems a few of these are inactive when high and active when low?
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As you surmise, it means that the function the pin name implies is active when low.
For example, /INT is low to trigger an interrupt and /WR is low to indicate a write.
answered Apr 26 '18 at 17:45
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2\$\begingroup\$ I'm surprised you didn't use the word "inverted". Basically, it means "not". While WR would mean the pin denotes that writing has been enabled when it is held high, /WR means that writing has been enabled when it is held low. Essentially an inversion. Or you could reinvert it by including a NOT gate in front of it. Not that you'd want to do that, just that it helps to explain it. \$\endgroup\$ – Octopus Feb 12 '19 at 21:10
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It usually means an active low pin.
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\$\begingroup\$ "usually"? When is it otherwise? :) \$\endgroup\$ – user103380 Apr 26 '18 at 18:03
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4\$\begingroup\$ When technical writers don't follow established standards. \$\endgroup\$ – Lior Bilia Apr 26 '18 at 18:25
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\$\begingroup\$ When technical writers use Microsoft Word and can't place an overheat without great gnashing of teeth, they will use a trailing \, *, or append _b. It is horrible to read. \$\endgroup\$ – TimB Apr 26 '18 at 19:48
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\$\begingroup\$ Sometimes we stick a lower-case n at the front or back, unfortunately netlists don't handle over bars very well. \$\endgroup\$ – Spehro Pefhany Apr 26 '18 at 20:14
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