Introducing Interrupts - Revision history

Mr z: Protected "Introducing Interrupts" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

2010-12-04T08:42:46Z

Protected "Introducing Interrupts" ([edit=autoconfirmed] (indefinite) [move=autoconfirmed] (indefinite))

2008-09-08T15:54:59Z

‎Putting it All Together

2008-09-08T15:53:52Z

‎Putting it All Together

2008-09-08T15:53:19Z

‎The Rest

2008-09-08T15:52:41Z

‎The Wait Code

2008-09-08T15:43:04Z

‎Step 3: Displaying the time

2007-12-29T02:24:14Z

‎Clearing the Screen

2007-12-25T17:58:44Z

‎What Happens When the CPU Takes an Interrupt?

2007-12-03T09:13:34Z

‎Step 2: Take a snapshot of the time

2007-12-03T09:08:58Z

‎Critical Sections

@@ Line 709: / Line 709: @@
 and INCLUDE directives for all of the library functions.  This particular
 example needs
-<CODE>[http://sdk-1600.spatula-city.org/examples/library/fillmem.asm fillmem.asm]</CODE>
+<CODE>[[fillmem.asm]]</CODE>
 and
-<CODE>[http://sdk-1600.spatula-city.org/examples/library/prnum16.asm prnum16.asm]</CODE> from SDK-1600.  Download these files and put them in a directory.
+<CODE>[[prnum16.asm]]</CODE> from SDK-1600.  Download these files and put them in a directory.
 Then put the following source code in a new file named <CODE>elapsed.asm</CODE>
 in the same directory.  This source code contains all of the snippets from

@@ Line 1,026: / Line 1,026: @@
 The source listing below puts all the fragments above into a complete program.
 Mainly, this just adds the cartridge header, the <CODE>INCLUDE</CODE>
-directives to include
+directives to include [[print.asm]] and [[fillmem.asm]]
 from SDK-1600, and assigns <CODE>WTIMER</CODE> a location in 8-bit memory.
 The bold portions are the new portions.

@@ Line 982: / Line 982: @@
 as we did previously in the [[Hello World Tutorial]].  We'll also use the
 an infinite loop.  We'll reuse [http://sdk-1600.spatula-city.org/ SDK-1600's]
-[http://sdk-1600.spatula-city.org/examples/library/print.asm PRINT] and [http://sdk-1600.spatula-city.org/examples/library/fillmem.asm CLRSCR]
+[[print.asm|PRINT]] and [[fillmem.asm|CLRSCR]]
 functions.  This results in the following code:

@@ Line 947: / Line 947: @@
 for the number of tics specified in the word after the <CODE>[[CALL]]</CODE>.
 (See
-[http://intelliwiki.kylesblog.com/index.php/Introducing_the_Instruction_Set_Part_3#Passing_Arguments_via_Return_Address the branch tutorial] for an explanation of this technique.)  The second entry
+[[Introducing_the_Instruction_Set_Part_3#Passing_Arguments_via_Return_Address|the branch tutorial]] for an explanation of this technique.)  The second entry
 point expects the number of tics to wait to be in R0.
@@ Line 976: / Line 976: @@
           [[JR]]      R5                  ; return
           ENDP
 == The Rest ==

@@ Line 465: / Line 465: @@
 To display the time, we'll use the [http://sdk-1600.spatula-city.org/ SDK-1600]
 routine <CODE>PRNUM16</CODE>, found
-[http://sdk-1600.spatula-city.org/examples/library/prnum16.asm here].  The
+[[prnum16.asm|here]].  The
 <CODE>PRNUM16.z</CODE> routine prints the number in R0 in a fixed width field,
 complete with leading zeroes.  It prints the value to the screen, starting at

← Older revision	Revision as of 08:42, 4 December 2010
(No difference)

@@ Line 676: / Line 676: @@
 with 0 as well.  It seems like we should be able to combine the two acts.
 <br/><br/>
-It turns out we can.  Addresses $01F0 - $01FF refer to the [[Programmable
+It turns out we can.  Addresses $01F0 - $01FF refer to the [[Programmable Sound Generator]] (aka. PSG).  We can safely write 0s to all of its locations.
 In fact, this is the preferred way to initialize the PSG when its state is
 otherwise unknown.  Thus, we can combine the <CODE>FILLZERO</CODE> and
@@ Line 691: / Line 690: @@
 us already.)
 <br/><br/>
 === Setting up the Interrupt Handler ===

@@ Line 79: / Line 79: @@
          when we return from the interrupt.
      </LI>
-     <LI>The CPU then jumps to location $1004.  The hardware determines
+     <LI>The CPU then jumps to location $1004.  The hardware sets
          this address, and there's no easy way to change this address on
          the Intellivision.

@@ Line 438: / Line 438: @@
 interrupts and read the time with interrupts off.  This copy of the time
 is guaranteed to be consistent no matter what.  For the purposes of this
-example, we'll read the time and put a copy of it on the stack with [[PSHR]].
+example, we'll read the time and put a copy of it on the stack with <CODE>[[PSHR]]</CODE>.
           [[DIS]]                     ; Disable ints (begin critical section)

@@ Line 210: / Line 210: @@
 call analogy above, this is similar to carrying a hot bowl of soup:  You
 don't want to spill the soup, and carrying it requires your full attention,
-so you want to do so without interruption.
+so you want to do so without interruption until you safely set down the soup.
 <br/><br/>
 To fix the example above, you can wrap the critical code with