Xilinx EDK 8.2i ble

MicroBlaze Processor Reference Guide www.xilinx.com 85

UG081 (v6.0) June 1, 2006 1-800-255-7778

Instructions R

ble Branch if Less or Equal

Description

Branch if rA is less or equal to 0, to the instruction located in the offset value of rB. The

target of the branch will be the instruction at address PC + rB.

Themnemonic bled will set the D bit. The D bit determines whether there is a branch delay

slotor not. If the D bit is set, it means that there is a delay slot and the instruction following

thebranch (i.e. in the branch delay slot) is allowed to complete execution before executing

the target instruction. If the D bit is not set, it means that there is no delay slot, so the

instruction to be executed after the branch is the target instruction.

Pseudocode

If rA <= 0 then

PC ←PC + rB

else

PC ←PC + 4

if D = 1 then

allow following instruction to complete execution

Registers Altered

•PC

Latency

1 cycle (if branch is not taken)

2 cycles (if branch is taken and the D bit is set)

3 cycles (if branch is taken and the D bit is not set)

Note

A delay slot must not be used by the following: IMM, branch, or break instructions. This

also applies to instructions causing recoverable exceptions (e.g. unalignement), when

hardware exceptions are enabled. Interrupts and external hardware breaks are deferred

until after the delay slot branch has been completed.

ble rA, rB Branch if Less or Equal

bled rA, rB Branch if Less or Equal with Delay

1 0 0 1 1 1 D 0 0 1 1 rA rB 0 0 0 0 0 0 0 0 0 0 0

0 6 11 16 21 31

Contents

Main Page MicroBlaze Processor Reference Guide UG081 (v6.0) June 1, 2006 Page Preface: About This Guide Chapter 1: MicroBlaze Architecture Chapter 2: MicroBlaze Signal Interface Description Chapter 3: MicroBlaze Application Binary Interface Chapter 4: MicroBlaze Instruction Set Architecture Preface About This Guide Manual Contents Additional Resources Conventions Typographical Online Document Page Chapter 1 MicroBlaze Architecture Overview Features Page Data Types and Endianness Instructions Page Page Page Page Page Page Registers General Purpose Registers Special Purpose Registers Program Counter (PC) Machine Status Register (MSR) Page Exception Address Register (EAR) Exception Status Register (ESR) Branch Target Register (BTR) Floating Point Status Register (FSR) Processor Version Register (PVR) Page Page Page Pipeline Architecture Branches Delay Slots Memory Architecture Reset, Interrupts, Exceptions, and Break Reset Hardware Exceptions Exception Causes Breaks Hardware Breaks Software Breaks Interrupt User Vector (Exception) Instruction Cache General Instruction Cache Functionality BRAM Tag Instruction Cache Operation Data Cache General Data Cache Functionality Data Cache Operation Tag BRAM Data Cache Software Support Floating Point Unit (FPU) Format Rounding Operations Arithmetic Comparison Fast Simplex Link (FSL) Hardware Acceleration using FSL Debug and Trace Debug Overview Trace Overview f Page Chapter 2 MicroBlaze Signal Interface Description Overview Features MicroBlaze I/O Overview Page Page On-Chip Peripheral Bus (OPB) Interface Description Local Memory Bus (LMB) Interface Description LMB Signal Interface Addr[0:31] Byte_Enable[0:3] Page LMB Transactions Generic Write Operation Generic Read Operation Back-to-Back Write Operation Single Cycle Back-to-Back Read Operation Back-to-Back Mixed Read/Write Operation Read and Write Data Steering Fast Simplex Link (FSL) Interface Description Master FSL Signal Interface Slave FSL Signal Interface FSL Transactions FSL BUS Write Operation Xilinx CacheLink (XCL) Interface Description CacheLink Signal Interface CacheLink Transactions Instruction Cache Read Miss Data Cache Read Miss Data Cache Write Debug Interface Description Trace Interface Description Page MicroBlaze Core Congurability Page Page Page Chapter 3 MicroBlaze Application Binary Interface Scope Data Types Register Usage Conventions Stack Convention Page Calling Convention Memory Model Small data area Data area Common un-initialized area Literals or constants Interrupt and Exception Handling Chapter 4 MicroBlaze Instruction Set Architecture Summary Notation Formats Type A Type B Instructions add addi and andi andn andni beq beqi bge bgei bgt bgti ble blei blt blti bne bnei br Page bri Page brk brki bs bsi cmp Chapter 4: MicroBlaze Instruction Set Architecture fadd This instruction is only available when the MicroBlaze parameter C_USE_FPU is set to 1. The oating point sum of registers rA and rB, is placed into register rD. 4 cycles fadd rD, rA, rB Add frsub fmul MicroBlaze Processor Reference Guide www.xilinx.com 103 UG081 (v6.0) June 1, 2006 1-800-255-7778 Instructions fdiv This instruction is only available when the MicroBlaze parameter C_USE_FPU is set to 1. 28 cycles fdiv rD, rA, rB Divide 0 1 0 1 1 0 rD rA rB 0 0 1 1 0 0 0 0 0 0 0 0 6 11 16 21 31 fcmp Page get idiv imm lbu lbui lhu lhui lw lwi mfs msrclr msrset mts mul muli or ori pcmpbf pcmpeq pcmpne put rsub rsubi rtbd rtid rted rtsd sb sbi sext16 sext8 sh shi sra src srl sw swi wdc wic xor xori