Re[2]: [stella] I'm looking through 6 digit code

Subject: Re[2]: [stella] I'm looking through 6 digit code
From: zu03776 <zu03776@xxxxxxxxxxxxxxxxxx>
Date: Mon, 19 May 2003 00:48:58 -0500
AB> Alright, obviously I should have read a bit further... "zero" refers to
AB> a memory location, but I still don't know what the  #> thing does.

The <zero and >zero indicate to take the lower- and upper- half of the
address.  The # in front indicates to use the immediate addressing

As an example, say that the label zero points to address $1234.  The
'>zero' operation would return the value $12, and '<zero' would return
>$34.  The operators return the high byte and low byte of a memory

The reason for the # sign is so that the value is loaded into the
accumulator, as opposed to the contents of the memory location
indicated.  That is, we want (from previous example) the value $12 in
the accumulator, and not the contents of memory location $12.

There is an easier-to-read mnemonic for this operation which escapes
me completely.  It is part of the new DASM compiler or the new
vcs.h header file.  I'm just used to using the > and < symbols.

I've probably made this more confusing than necessary; if you're still
confused someone may do a better job of explanation.

>> I'm looking through Robin Harbron's 6-digit routine and I've come
>> across some code I don't understand.
>>         asl
>>         adc #<zero
>>         sta ptr0,y
>>         lda #0
>>         adc #>zero
>>         sta ptr0+1,y
>> What do the arguments "#<zero" and  "#>zero" actually mean? The two
>> books, I have don't say anything about it, and the dig's search engine
>> won't let me do a search on the greater than symbol. I guess it seems
>> to assemble... does this just tell the assembler to use any number
>> greater or less than zero?

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