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From: Spehro Pefhany
Subject: Re: Digital Design
References: <191C91BDFE8ED411B84400805FBE794C33104B6F@pfs21.ex.nus.edu.sg> <-fecnUeOzY9yvrGjXTWc3Q@comcast.com>
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Date: Mon, 20 Jan 2003 16:39:23 GMT
NNTP-Posting-Date: Mon, 20 Jan 2003 11:39:23 EST
On Mon, 20 Jan 2003 11:29:32 -0500, the renowned "Charles Schuler"
>"Dave Orchard" wrote in message
>> Hey all
>> I have to do a digital design project to create a simplifed Taxi fare
>> using logic gates
>> Any introduction website or book to recommened to start me off!
>> Dave Orchard
>I have spent little time in Taxis but seem to recall that the display
>advances faster as miles are accrued.
Usually there is a fixed "flagfall" amount for the first x.x km and
then a certain amount more for each additional unit of distance.
(substitute 1/8 mile for metric units in the USofA).
Often there are switches to increase the rate during rush hour or at
night (beware if you're not literate in the local language these
are not switched at inappropriate times), and perhaps switches for
bags, tolls or other extras.
There's also a charge for "waiting time", and I'm not sure how
that figures into the normal driving time, whether it automatically
comes into play when the wheels stop or whether it has to be manually
switched on. But you could probably forget about this, and just go
with distance for a school project.
>So, it seems that an up-counter driven by an OR gate with two inputs:
>pulses from an astable (clock)
>and pulses from the odometer sensor. Then, add the display drivers and
>decoders and a reset circuit.
I think you'd need a down counter operated by the odometer, preset
initially (flagfall) to the first distance then to the incremental
distance. The money register could be counter as well, and could
be preset to the initial amount, and then a certain number of counts
added on for each tick from the prescaler. You could also do it with
adders, but the counter will yield less parts.
"it's the network..." "The Journey is the reward"
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