arblogic.doc : 28 Aug 97
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Revision Info
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v1.0 - Freeware release
	First release


Description
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arblogic is a utility for generating hex files for programming EPROMs with 
arbitrary combinatorial logic. It has a simple but effective RPN-based 
expression input. 


Application
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The basis of expression input is reverse polish notation (RPN). This allows 
a very easy stack-based evaluation to take place with the minimum of parsing 
and conversion. 

Suppose you wanted output D0 to be the logical AND of inputs A0 and A1. (A0 
means address line 0; this should be labelled in the data sheet for the 
EPROM).

The expression A0A1&D0 achieves this. The first two commands A0A1 push the 
value of A0 and A1 on to the stack. The command & ANDs together the top two 
stack locations and replaces them with the result. The command D0 pops the 
top stack location into D0. That's it. 

The commands available for logical operations are 

& - AND
| - OR
! - NOT

Below is an example of a set of RPN strings for a device :

A1A2!A3A0|&&D0
A1A2A0&&D1
A1A2!A3&&D2
A0D3

(See arblogic.xcl for the full file, which is mostly comments.)

These were implemented using a 27C64 and also a 27C128 (whatever I had 
hanging around), and performed right first time. This is a cheap way for 
designers to have some of the basic advantages of PLDs :

	Field Upgrades
	Product line expansion by using different EPROMs
	Re-design and re-route without changing the PCB artwork
	Arbitrary logic without loads of packages

Strings can be entered on the command line but it is more useful to use an 
XCL file, and run the program with arblogic -x. See the attached file. 
Comments follow # characters. 

Arblogic ignores anything it can't understand, so it's OK to use spaces to 
improve readibility. A1A2 is the same as A1 A2 is the same as A1,A2,

The highest address required is detected and code is only generated up to 
that point. This makes for small hex files and quick programming. Note that 
addresses from A10 to A15 should be entered with a lower case hex digit, ie 
Aa to Af. 


Limitations
-----------

This package is very limited. As far as function is concerned I do not want 
to take it much further but I would like to improve the user interface by 
providing labelling, other output formats, and possibly a more natural 
expression entry (but once you've got used to RPN, you'll find it easy and 
intuitive). 


Bugs
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None known.


License
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See attached file license.doc. 


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mikepage@iee.org