Splitter appearance
C Burch
it's probably better to open it up to discussion. Attached I've drawn
four proposals for how splitters should appear in Logisim.
Alternative A: This is the current technique. The main disadvantage is
that it doesn't leave any room for labels showing how each split end
corresponds to bits from the combined end. It could also be described
as ugly. It has the advantages of being consistent with previous
versions, of being a minimal design, and of taking up less room in the
circuit than the alternatives.
Alternative B: This is a minimal change to A that would allow labels
to be added.
Alternative C: This difference between B and C is that C has a
different placement of the combined end relative to the split ends. I
think C matches more closely how this concept would normally be
represented in a traditional circuit diagrams. However, C would
require people to rewire circuits if they wanted to convert everything
over to use the new appearance instead. (However, as in the current
fragile release, Logisim would continue to offer A as an alternative,
and files created using old versions would load up using the older
splitter appearance.)
Alternative D: This is the "Trapezoid" technique used in the current
fragile release. It's a more marked departure from the previous
appearance, is perhaps less intuitive, and is prone to be confused
with a multiplexer. The advantage is that without all the individual
lines going into each split end, the labels can be read more easily.
Would anybody comment on which you'd prefer? Or would anybody like to
propose an Alternative E?
-Carl
On Sat, Feb 26, 2011 at 5:34 PM, Ilia Lilov <lil...@gmail.com> wrote:
> So, Carl, do you think it's time to remake screen shots? If so, we
> need the last fragile release with the recent few GUI strings
> translated for screen shots (at least me and Thanos).
>
> I know it's all about human conservatism, but I feel sad a bit about
> default Splitter appearance change. I really loved old one. I know
> labels with ends numbers are incredibly handy, but I think old
> appearance was more intuitive for understanding what splitter does.
> I'm not going to be obstacle for progress of course, but I want to
> ask: are you sure about this change, Carl? Aren't you afraid of
> old-timers' screams? (It's some kind of semi-serious joke).
>
> Ilia.
>
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Thanos Kakarountas
tools I have used in the past. What I haven't tried yet is to combine 2
splitters to create sub-buses from a wide system bus (used in computer
architecture, when reading operands directly from the opcode). However,
alternative C is probably the most handy splitter even for this work
C Burch
If you wanted to create "sub-buses" from a wider bus using Alternative
C, you'd have two ways of doing that, each diagrammed in the attached
"splitter-join.png" file. The first version is probably what you're
imagining, Thanos, and I think it works reasonably well. However, I'd
suggest instead creating a splitter whose Data Bits attribute is 4 and
whose Fan Out is 2 and modifying the individual "Bit x" attributes as
you would like; that would be drawn as with the second version
illustrated. (Logisim has supported these attributes for splitters for
a very long time. However, because of how splitters have drawn, some
people have advocated always having the Fan Out match the Data Bits
attribute.)
An issue when you have several bits feeding into the same split end is
that the label associated with that split end can get longer than the
space that is available. In the current fragile release, there is a
choice between "Trapezoid" and "Fat Trapezoid," where the "fat"
trapezoid leaves more room for longer labels (with more horizontal
distance between the split ends and the combined end). This is an
issue with any of the alternatives B through D, and the same type of
choice would remain.
I've remembered another problem with the current drawing technique -
and with Alternative B: What happens when the Fan Out attribute is 1?
I've enhanced my "splitters.png" image to show how that appears for
each of the alternatives. With A and B, you have something that is can
hardly be distinguished from a short wire. With C and D, you get
something that still definitely looks like a splitter.
crc pucmg
Ilia Lilov
My first acquaintance with splitters was in my childhood, when I
turned over the pages of soviet magazine "Modelist Konstruktor, 1990",
which my father was subscribed to. I have attached a page from that
magazine with the random circuit containing a bus (it shown as bold
line). It almost exactly matches to Carl's alternative C with two
exclusions: 1) there are no diagonal segment there; 2) number label of
split end is at the top of corresponding end, not on the bottom of it.
However, it isn't very important; moreover, I think diagonal segment
rises readability of the circuit. So, my vote is for alternative C
too: with this one we have number labels and intuitive understanding
what splitter does at the same time.
Also I think it's very good idea to keep alternative A for the
compatibility (and for old-timers' calmness), and also to have
alternative B as intermediate alternative between A and C: B has the
same handy labels as C does, but also has complete shape compatibility
with old appearance (A), so one doesn't have to remake his circuits.
Ilia.
