Skip to content

BRA.md

Latest commit

 

History

History
62 lines (52 loc) · 1.66 KB

BRA.md

File metadata and controls

62 lines (52 loc) · 1.66 KB

Branch

Uses: GOTO, CALL

Mnemonics:

  • GO TO
  • CALL

Description:

Branch (goto) another point in the code and continue execution. Functionally equivalent to moving into the PC.

Condition Codes:

Flag Modified
Carry ✗
Negative ✗
Overflow ✗
Zero ✗

Notes:

  • May use a symbol optionally instead of an address offset

Examples:

CALL &Ry    ; branch to address in Ry after performing a link
            ; a.k.a: LR <- PC, PC <- Ry
GOTO 0x40   ; branch to address (PC + 0x40)
            ; a.k.a: PC <- PC + 0x40
CALL _foo   ; branch and link to the symbol `_foo`
            ; (performs a procedure call)

Format (Op2):

│15   11│10 │9  8│ 7 │6   4│3    0│
┌───────┬───┬────┬───┬─────┬──────┐
│ 00000 │ L │ -- │ 0 │ --- │ YYYY │
└───────┴───┴────┴───┴─────┴──────┘

Format (Imm):

│15   11│10 │9  8│ 7 │6       0│
┌───────┬───┬────┬───┬─────────┐
│ 00000 │ L │ -- │ 1 │ DDDDDDD │
└───────┴───┴────┴───┴─────────┘

Legend:

Format Use
0, 1 Literal bit
D Immediate data
L Link flag
Y Source Ry
- Unused

Link (L):

When set, "link" on the branch. (Copies PC <- LR before performing the branch.)