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'retlw'
1997\02\13@215132 by ONY NIXON 54964

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Thanks for the help with the retlw table writes. My fingers might now
stop looking like they belong to ET.

What is the point of the 'Data' directive for MPASM. Looking at the
code it generates, I can't see any use for it.
Eg
Data 1h, 2h, 3h, etc

generates

0001, 0002, 0003 etc

Tony


Just when I thought I knew it all,
I learned that I didn't.

1997\02\13@222447 by John Payson

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> What is the point of the 'Data' directive for MPASM. Looking at the
> code it generates, I can't see any use for it.
> Eg
> Data 1h, 2h, 3h, etc  generates  0001, 0002, 0003 etc

The data directive is useful for precisely those instances where you wish
to place something specific into the hex file which will not be used by
the firmware itself but may be used by the programmer ["burner"] or other
such tools.

For example, someone might wish to place information about the chip in ASCII
format near the start or end of its memory map.  On, e.g., a 16C84 device
any byte whose most significant 7 bits are zero will read out unchanged even
if the device itself is code-protected.  Thus, if information about the chip,
author, copyright, revision, etc. were placed in ASCII near the start of the
chip it could easily be read out (even after code-protection) and viewed on
screen.

Alternatively, while there is no standard for this, it would be possible for
a programmer to use a convention that [for anything other than a 12C50x or
16C5x] the last location in RAM indicates the type of device, its pinout (if
needed), its memory size, and whether it is EPROM or EEPROM based.  The
programmer could then use this information to inform the user what type of
chip they should insert, and reduce the risks of damaging chips by user error
(for example, programming a bunch of 622's, having to do a couple of '84's for
another project, and then programming another 622 without remembering to set
the programmer for EPROM mode again).

Does anyone know whether there's any possibility that Microchip might "bless"
the use of such an address and recommend support for it in new programmers?
It would not require any silicon change--just a documentation change--but it
would reduce the number of destroyed window parts...

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