8051 jbc instruction help
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8051 jbc instruction help

 
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PagCal
Guest
Posted: Wed Dec 14, 2005 4:19 pm    Post subject: 8051 jbc instruction help Reply with quote
jump if bit set and clear (jbc) has 3 bytes:

0x10 - the instruction
0xbit - the bit number
0xoff - the relative pc offset to take if bit set

the question is, which pc is the 'off' relative to?

In other words, if my program has:

pc code
-------------
5 0x10
6 bit
7 off

is the 'off' relative to pc = 7 or pc = 8 or some other pc?
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Meindert Sprang
Guest
Posted: Wed Dec 14, 2005 4:47 pm    Post subject: Re: 8051 jbc instruction help Reply with quote
"PagCal" <pagcal@runbox.com> wrote in message
news:glSnf.77$Vr.73@fe06.lga...
Quote:

jump if bit set and clear (jbc) has 3 bytes:

0x10 - the instruction
0xbit - the bit number
0xoff - the relative pc offset to take if bit set

the question is, which pc is the 'off' relative to?

In other words, if my program has:

pc code
-------------
5 0x10
6 bit
7 off

is the 'off' relative to pc = 7 or pc = 8 or some other pc?

Well, the datasheet says: "The range of the jump is therefore -128 to +127
Program Memory bytes relative to the first byte following the instruction."
So, it is relative to pc = 8.

Meindert
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