Re: A86: RST 10


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Re: A86: RST 10



At 04:13 PM 9/23/97 -0400, you wrote:
>In a message dated 97-09-23 15:19:40 EDT, you write:
>
>> 
>>  can someone tell me how to use RST commands and what exactly they're used
>>  for? sorry this is proably basic stuff to ya'll.  all i know about them is
>>  that they're used to find things in memory right?
>>  
>>  thanx,
>>  Patrick
>>  
>>  
>
>Restarts are used to call locations in ROM that are called commonly.  RST 20h
>and RST 10h both deal with finding variables.  I believe 00h has something to
>do with formatting the calc, or maybe a self test.  Anyway, they go all the
>way from 00h to 40h in increments of 8h. (00h,08h,10h,18h, etc).  I think
>they actually call that address in rom but are faster or more efficient or
>something. (someone correct me if I'm wrong)  Once I get my Z80 books (if
>_ever_) then I can tell you more about it... :-(
>
>~Stephen Hicks
>
>

Yeah, you're exactly right.  TI just put commonly used routines at those
entry points.  The reason is because <rst 10h> is 2 bytes shorter than
<call $0010> and those bytes can add up.

RST $10 finds the variable whose id, length, and name are in op1
RST $20 puts the variable id, length, and name into op1

RST $00 does start the calc, because that is the initial code started when
calc is started. (actually only when batteries are taken out and back in)


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 Alan Bailey            mailto:bailela@charlie.cns.iit.edu
 IRC:Abalone              Web:http://www.iit.edu/~bailela/
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