Difference between revisions of "Return Stack"
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* Last-In, First-Out (LIFO) | * Last-In, First-Out (LIFO) | ||
** [https://github.com/dominiksalvet/vhdl-collection/blob/master/rtl/lifo.vhdl VHDL code] | ** [https://github.com/dominiksalvet/vhdl-collection/blob/master/rtl/lifo.vhdl VHDL code] | ||
| − | * | + | * 12-bit width |
| − | ** 0 | + | |
| + | == Configuring Depth == | ||
| + | |||
| + | * Configurable stack depth | ||
| + | ** 0 = no stack | ||
*** No JSRs or RTSs in code | *** No JSRs or RTSs in code | ||
*** Can do JMPs | *** Can do JMPs | ||
| − | ** 1 deep | + | ** 1 deep = Single deep calls |
| − | |||
| − | |||
** Optionally deeper as build option (uses more registers) | ** Optionally deeper as build option (uses more registers) | ||
| − | |||
| − | |||
| − | |||
* Set STACK_DEPTH_PASS to the max nesting depth of the subroutines in the top file | * Set STACK_DEPTH_PASS to the max nesting depth of the subroutines in the top file | ||
* The LIFO capacity is equal to 2 ^ STACK_DEPTH_PASS | * The LIFO capacity is equal to 2 ^ STACK_DEPTH_PASS | ||
Revision as of 14:54, 19 April 2022
IOP-16 Stack
- Stack is used to keep track of return addresses for subroutines
- Stores to stack on JSR instruction
- Loads from stack with RTS instruction
- Last-In, First-Out (LIFO)
- 12-bit width
Configuring Depth
- Configurable stack depth
- 0 = no stack
- No JSRs or RTSs in code
- Can do JMPs
- 1 deep = Single deep calls
- Optionally deeper as build option (uses more registers)
- 0 = no stack
- Set STACK_DEPTH_PASS to the max nesting depth of the subroutines in the top file
- The LIFO capacity is equal to 2 ^ STACK_DEPTH_PASS
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
- STACK_DEPTH_PASS = 4
- ALMs: 54
- Registers: 158
