Difference between revisions of "Return Stack"
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Blwikiadmin (talk | contribs) (Created page with "= IOP-16 Stack = * Sizes ** 0 (none) *** No JSRs or RTSs in code *** Can do JMPs ** 1 deep (does not need SRAM) *** Single deep calls ** Optionally deeper as build option (us...") |
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= IOP-16 Stack = | = 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) | ||
| + | ** [https://github.com/dominiksalvet/vhdl-collection/blob/master/rtl/lifo.vhdl VHDL code] | ||
| + | * 12-bit width | ||
| + | |||
| + | == 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 | + | * 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 - 1 | ||
| + | |||
| + | <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 == | ||
| + | |||
| + | * STACK_DEPTH_PASS = 3 | ||
| + | ** ALMs: 33 | ||
| + | ** Registers: 86 | ||
| + | * STACK_DEPTH_PASS = 4 | ||
| + | ** ALMs: 54 | ||
| + | ** Registers: 158 | ||
Latest revision as of 15:01, 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 - 1
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 = 3
- ALMs: 33
- Registers: 86
- STACK_DEPTH_PASS = 4
- ALMs: 54
- Registers: 158
