Subject:
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HandyBoard Expansion.....
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 21 Nov 1996 00:13:43 GMT
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Original-From:
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Scott Seaton - CMC Engineer <scotts@smeg.aus(NoMoreSpam).sun.com>
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Viewed:
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1214 times
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Hi
I'm roughing out a design to add some more(*) IO to my handyboard and have run
into a slight problem....
I'm going to have another 4 devices on the data bus, 2 x 74HC574 & 2 x 74HC541.
Will this exceed the "fan out" of the cpu ? (I don't have the "A" series ref.
manual - is there one ? I have the E & F series books.)
I think that it probably will, so I'm looking at buffering the data bus using
a 74HC245. Does anyone know how I can interface this with the HC11 ? I know
that the R/W line should be connected to the DIR input of the '245, but what
should I connect the E (inverting) enable input to ?
Are there any problems using HCT devices with the HandyBoards HC components ?
How much information does the the M68HC11RM/AD (the 68HC11 Reference Manual)
contain ? Is it just a general usage guide or does it have more detail like
code examples / sample circuits etc ?
* Here's what I plan to add to my HandyBoard:
1 x 8bit counter & Latch (2 x 74HC161 + 1 x 74HC541) for speed sensing etc
1 x 8bit Latch (1 x 74HC574) for 8 general purpose outputs
1 x 8bit Input (1 x 74HC541) for 8 general purpose inputs
1 x 8bit Latch (1 x 74HC574) used for Analog Mux & IR Proximity drivers
1 x 8 Input Analog Mux
IR Proximity drivers (1 x 555) with 2 ranges
Microphone + amplifier
Sonar connector for TOC3 with buffered power supply
Buffered 5V supply for a Polaroid Sonar
I'm using the '574 rather than the '374 because the input/output lines are on
opposite sides of the chip (easier to layout the pcb). I'm also using the '541
instead of the '244 for the same reason - I don't have much data on the '541,
does anyone know of any reasons why the '541 can't be used ?
I'll be using the Protel demo software (no save :( ), but I'll try to put
together some information and the postscript files for those that are
interested. I'll be making the board at home, using the "laserprinter and OHP
film" method, so the board design will be tailored towards ease of
construction (for me ....).
Would anyone like gerber/drill files if I can generate them ?
Thanks
Scott
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