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'[SX]: IREAD instruction'
2002\05\27@070808 by ISO-8859-1?Q?Ruben_J=F6nsson?=


I have found a strange thing with the IREAD instruction in an
SX52 chip. When the IREAD is set up to read the word at address
$802 + the address of the IREAD instruction itself, it allways
returns $cff.

Could someone please test this and verify my results. Here is a
code snippet that demonstrates this:


       FREQ    10_000_000
       RESET   Startup

       org     $0a

       ROM_L           DS      1
       ROM_H           DS      1

       org     0
       mov             ROM_L,#(string & $ff)
       mov             ROM_H,#(string >> 8)
       mov             w,ROM_H
       mov             m,w
       mov             w,ROM_L
       test            w
       jmp             $
       ; doesn't do anything usefull with w.
       inc             ROM_L
       inc             ROM_H
       jmp             loop

       org     $800

       dw              'ABCDEFGHIJKLMNOPQRSTUVWXYZ',0

This is assmebled, programmed and single stepped with the SX-
Key Rev E.

The IREAD fails when it is reading the 'J' from the string. The
IREAD instruction is at address $007 and the 'J' is at address

Ruben Jvnsson
AB Liros Electronic
Box 9124, 200 39 Malmv, Sweden
TEL INT +46 40142078
FAX INT +46 40947388

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2002\05\27@121001 by James Newton, webmaster

face picon face

What is the date code on the SX52? Some older versions are not
supported with the SX-Key Rev E.

Is the failure reliable? If not, it may be a communications
failure between the SX-Key and the PC or excessive noise or bad
connection between the key and 52. I've seen a lot of "strange"
things with SX-Keys.

Try a test program that counts up a register from "A" and
compairs it with the data from the IREAD and turns on an LED if
they don't match, then run it off the SX-Key. If it works,
consider replaceing the SX-Key with rev F (latest) from Parallax
Inc or switch to the SX-DEV.

James Newton: webmaster, former Admin #3  1-619-652-0593 phone

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