18_Branch_Manager.md

Branch Manager

Contents

• Inputs
• Outputs
• Functionality
  • Registers
  • Combinational
  • Clk
  • Active low reset

Inputs

Name	Bits wide
clk	1-bit
rstn	1-bit
pred_taken	1-bit
pred_pc	32-bits
pred_addr	32-bits
act_taken	1-bit

Outputs

Name	Bits wide
flush	1-bit
npc	32-bits

Functionality

Registers

• 1-bit restart register
• 32-bit npc register
• 1-bit flush register

On posedge clk

• If (pred_taken != act_taken)&&(!restart)
  • flush = 1
  • act_taken

    act_taken	npc
    act_taken == 0	npc = pred_pc + 4
    act_taken == 1	npc = pred_addr

• Else
  • flush = 0
  • pred_taken

    pred_taken	npc
    pred_taken == 0	npc = pred_pc + 4
    pred_taken == 1	npc = pred_addr

• If restart, restart = 0

Asynchronous active low reset

• restart set to 1
• All other registers set to 0