Negative logic - Revision history

Jnc: fix link

2019-11-22T20:24:27Z

fix link

Jnc: better cat

2018-12-16T20:52:46Z

better cat

Jnc: +cat

2018-12-14T20:16:28Z

+cat

Jnc: An OK start

2018-10-14T11:37:06Z

An OK start

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'''Negative logic''' has two meanings.

The current usual meaning is [[logic]] in which the [[voltage]]s for 'true' and 'false' are reversed; for example, with the [[transistor-transistor logic|TTL]] [[logic family]], true would be [[ground]], and false would be +5V. The term '''active low''' is often used for this meaning.

An older meaning is the use of negative voltages. For example, this is seen in [[Digital Equipment Corporation|DEC]]'s [[System Module]]s, which use -15V and +10V supplies, and use -3V for the standard 'true' output level, and ground for 'false'. These levels are found in the [[input/output|I/O]] [[bus]]ses of some early DEC computers, such as early [[PDP-8]]'s.

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 The current usual meaning is [[logic]] in which the [[voltage]]s for 'true' and 'false' are reversed; for example, with the [[transistor-transistor logic|TTL]] [[logic family]], true would be [[ground]], and false would be +5V. The term '''active low''' is often used for this meaning.
-An older meaning is the use of negative voltages. For example, this is seen in [[Digital Equipment Corporation|DEC]]'s [[System Module]]s, which use -15V and +10V supplies, and use -3V for the standard 'true' output level, and ground for 'false'. These levels are found in the [[input/output|I/O]] [[bus]]ses of some early DEC computers, such as early [[PDP-8]]'s.
+An older meaning is the use of negative voltages. For example, this is seen in [[Digital Equipment Corporation|DEC]]'s [[System Module]]s, which use -15V and +10V supplies, and use -3V for the standard 'true' output level, and ground for 'false'. These levels are found in the [[input/output|I/O]] [[bus]]ses of some early DEC computers, such as early [[PDP-8 family|PDP-8]]'s.
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 [[Category: Hardware Basics]]