Difference between revisions of "Return Stack"

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Line 9: Line 9:
 
*** 12-bit register
 
*** 12-bit register
 
*** Single deep calls
 
*** Single deep calls
** Optionally deeper as build option (uses SRAM)
+
** Optionally deeper as build option (uses more registers)
 +
 
 +
== Configuring Depth ==
 +
 
 +
* Set STACK_DEPTH_PASS to the max nesting depth of the subroutines in the top file
 +
 
 +
<pre>
 +
IOP16: ENTITY work.cpu_001
 +
-- Need to pass down instruction RAM and stack sizes
 +
generic map (
 +
INST_ROM_SIZE_PASS => 512, -- Small code size since program is "simple"
 +
STACK_DEPTH_PASS  => 4   -- Subroutine depth (not nested)
 +
)
 +
</pre>
 +
 
 +
== Resources ==
 +
 
 +
* Value = 4
 +
** ALMs: 54
 +
** Registers: 158

Revision as of 14:40, 19 April 2022

IOP-16 Stack

  • Last-In, First-Out (LIFO)
  • Sizes
    • 0 (none)
      • No JSRs or RTSs in code
      • Can do JMPs
    • 1 deep (does not need SRAM)
      • 12-bit register
      • Single deep calls
    • Optionally deeper as build option (uses more registers)

Configuring Depth

  • Set STACK_DEPTH_PASS to the max nesting depth of the subroutines in the top file
IOP16: ENTITY work.cpu_001
-- Need to pass down instruction RAM and stack sizes
	generic map 	( 
		INST_ROM_SIZE_PASS => 512, -- Small code size since program is "simple"
		STACK_DEPTH_PASS   => 4	   -- Subroutine depth (not nested)
	)

Resources

  • Value = 4
    • ALMs: 54
    • Registers: 158