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GeneralRe: Found my first silicon bug Pin
User 1502577517-Feb-21 7:59
User 1502577517-Feb-21 7:59 
GeneralRe: Found my first silicon bug Pin
GenJerDan18-Feb-21 1:05
GenJerDan18-Feb-21 1:05 
GeneralRe: Found my first silicon bug Pin
Mircea Neacsu18-Feb-21 1:47
Mircea Neacsu18-Feb-21 1:47 
GeneralRe: Found my first silicon bug Pin
Dave Kreskowiak17-Feb-21 7:57
mveDave Kreskowiak17-Feb-21 7:57 
GeneralRe: Found my first silicon bug Pin
Mircea Neacsu17-Feb-21 7:59
Mircea Neacsu17-Feb-21 7:59 
JokeRe: Found my first silicon bug Pin
20212a17-Feb-21 8:53
20212a17-Feb-21 8:53 
GeneralRe: Found my first silicon bug Pin
OriginalGriff17-Feb-21 8:55
mveOriginalGriff17-Feb-21 8:55 
GeneralRe: Found my first silicon bug - FINAL REPORT Pin
Mircea Neacsu17-Feb-21 9:32
Mircea Neacsu17-Feb-21 9:32 
As Griff was saying:
Quote:
Joy when I worked out what it was and reported it to the ops manager. Who just said "yeah, we know about that one..." and left me feeling very flat.


I worked it out what it is and here is my result.

Z80 processor has/had an instruction DJNZ that decrements register B and jumps if not zero. This is bread and butter of most small loops in Z80 assembly. It also has a set of "alternate" registers BC', DE' HL' but rather few instructions operate on those alternate registers. To compensate for this, Rabbit introduced an ALTD prefix that can be added to most instructions to make them operate on the alternate registers. Now what happens with the instruction ALTD DJNZ? Well, it takes the content of B register, decrements it and stores it in B' register making it a fairly useless instruction.

Of course, this is not documented in the manual and you have to figure it out for yourself.

Anyway, it left me feeling very flat Smile | :)
Mircea

GeneralRe: Found my first silicon bug - FINAL REPORT Pin
OriginalGriff17-Feb-21 10:09
mveOriginalGriff17-Feb-21 10:09 
GeneralRe: Found my first silicon bug - FINAL REPORT Pin
Randor 17-Feb-21 10:56
professional Randor 17-Feb-21 10:56 
GeneralRe: Found my first silicon bug - FINAL REPORT Pin
Mircea Neacsu17-Feb-21 11:00
Mircea Neacsu17-Feb-21 11:00 
GeneralRe: Found my first silicon bug - FINAL REPORT Pin
Randor 17-Feb-21 15:42
professional Randor 17-Feb-21 15:42 
GeneralRe: Found my first silicon bug - FINAL REPORT Pin
Mircea Neacsu17-Feb-21 16:14
Mircea Neacsu17-Feb-21 16:14 
JokeRe: Found my first silicon bug - FINAL REPORT Pin
Randor 17-Feb-21 16:37
professional Randor 17-Feb-21 16:37 
GeneralRe: Found my first silicon bug - FINAL REPORT Pin
Member 1292431218-Feb-21 3:01
Member 1292431218-Feb-21 3:01 
GeneralRe: Found my first silicon bug - FINAL REPORT Pin
Mircea Neacsu18-Feb-21 3:16
Mircea Neacsu18-Feb-21 3:16 
GeneralCalling Paul Griffin Pin
pkfox17-Feb-21 6:13
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JokeRe: Calling Paul Griffin Pin
User 1502577517-Feb-21 6:24
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GeneralRe: Calling Paul Griffin Pin
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GeneralRe: Calling Paul Griffin Pin
OriginalGriff17-Feb-21 6:45
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GeneralRe: Calling Paul Griffin Pin
RickZeeland17-Feb-21 6:45
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GeneralRe: Calling Paul Griffin Pin
OriginalGriff17-Feb-21 7:07
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GeneralRe: Calling Paul Griffin Pin
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GeneralLINQ is fun! Pin
Marc Clifton17-Feb-21 5:32
mvaMarc Clifton17-Feb-21 5:32 
GeneralRe: LINQ is fun! PinPopular
Dave Kreskowiak17-Feb-21 5:41
mveDave Kreskowiak17-Feb-21 5:41 

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