Subject:
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Question re hc374 Digital Out Solution
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Tue, 27 Jan 1998 23:00:21 GMT
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Original-From:
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Stephen Michael <stephen.michael@mci.comAVOIDSPAM>
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Reply-To:
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stephen.michael@mci.com/NoSpam/
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Viewed:
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2010 times
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I have already used the four digital outs on the SPI header and I
need more digital outputs from my HandyBoard. These questions
may show that I'm a neophyte as a hardware hacker, but I could
use some help.
In the HandyBoard FAQ under the question: "Does the Handy Board
have any digital outputs?", the following instructions are included:
* d0..d7 is the data bus and stuff is flying around on those pins all
the time,
* so they cannot be used as outputs. If you hook an ’hc374 chip to the
board,
* in the same fashion as the one driving the motor chips, you get 8 more
digital
* outs. Connect the ’hc374’s clock line to any of the three unused
output latch
* selects of the ’hc138 (Y0, Y2,or Y4). All of these signals are present
on the
* Expansion Bus.
Has anyone done this? Does this mean that, to get the additional 8
digital outs,
an 'hc374 should be connected as follows:
1. Pins 1D through 8D of 'hc374 connected to the HandyBoard's D0 through
D7?
2. Pins 1Q through 8Q are now the digital outs?
Is it really this simple? Should resistors or diodes be added to the
circuit? How
are the new outputs selected?
If this is off-base, can someone expand on the instructions in the FAQ?
I'd appreciate any assistance offered.
Stephen
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