17 Jun
2011
17 Jun
'11
2:38 p.m.
On 17 Jun 2011 at 2:41, Dan Roganti wrote:
This is going to be a holy war...
I find the 'assertion logic' symbols -- things like AND gates with
inverting bubbles on both inputsn and outputs (representing, say, a
quarter of a 7432 OR gate) -- jar somwhat when I look at a schemaitc. But
I have no problems realising thar ORing a couple of active-low signals
preforms a logical AND of them.
In other words :
This
IORQ/-----o|\
| >o------- I/ORd/
Rd/------o|/
'32
means I have to think for a milliseond
This
IORQ/------)\
) >------- I/ORd/
Rd/-------)/
'32
doesn;t
-tony
Positive Logic Design vs. Negative Logic
Design
Most moderately complex designs contain a mixture of both. What irks
me when reading a schematic is the idiot who assumes that a 7400 is
ALWAYS represented as a quad NAND gate. This sort of thinking, while
being bush-league, also obfuscates the actual circuit design.