Cortex-A8 Technical Reference Manual - ARM Information Center

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16.4.4 ThumbEE instructions Instruction Cycle Timing densely packed, slightly reducing the branch prediction accuracy that is achieved and therefore increasing the number of branch mispredictions. Neither of these effects can be accurately measured using hand calculating techniques. Note The code footprint and densely packed branch instructions can have an impact on the performance of the processor. In most cases, the interaction of these effects might cancel with each other. The majority of the ThumbEE instruction set is identical in both encodings and behavior to the Thumb-2 instruction set and therefore the cycle timings are also identical to the Thumb-2 instruction timings. The behavior of some instructions are different when executed in ThumbEE state instead of in Thumb state. However, the behavior changes for these instructions do not result in any changes to their cycle timing. The only additional cycle timing information for ThumbEE is for the new instructions. Table 16-17 shows the timing operation of the new ThumbEE instructions. ThumbEE memory check exceptions Table 16-17 ThumbEE instructions Instruction type Cycles Source1 Source2 Source3 Source4 Result1 Result2 ENTERX/LEAVEX a 16 - - - - - - CHKA b 1 E2 E2 - - - - HB c 1 - - - - - - HBL d 1 - - - - R14:E3 - HBP c 2 - - - - R8:E2 - HBLP d 2 - - - - R8:E2 R14:E3 LDR [R9] e 1 R9:E1 - - - Rd:E3 - LDR [R10] e 1 R10:E1 - - - Rd:E3 - LDR [negative offset] e 1 Rn:E1 - - - Rd:E3 - STR [R9] f 1 Rn:E1 Rd:E3 - - - - a. This instruction waits for all outstanding instructions to complete and then issues. b. If CHKA fails the array bounds check, then an exception is taken. Otherwise, this is a single cycle instruction. c. This instruction is predicted and behaves as a direct branch, B instruction. d. This instruction is predicted and behaves as a direct branch and link, BL instruction. e. Timing is identical to similar load instructions. f. Timing is identical to similar store instructions. All loads and stores in ThumbEE state have the additional functionality of checking the base register for a zero value. If the base register is zero, then the processor performs a branch to the address [HandlerBase – 4]. See the ARM Architecture Reference Manual for more information. The processor handles this scenario in the same way as to an exception such as a data abort because it does not occur in the common case. If the base register is zero, the processor flushes the pipeline and branches to the correct address. The additional cycle time penalty for this is ARM DDI 0344K Copyright © 2006-2010 ARM Limited. All rights reserved. 16-15 ID060510 Non-Confidential
16.4.5 Conditional instructions Instruction Cycle Timing variable in length, but is at least 13 cycles. The CHKA instruction uses the same mechanism when the array bounds check fails. This is also a rare occurrence and therefore is not optimized for performance. Predicting ThumbEE branch type instructions All ThumbEE branch type instructions are predicted in ThumbEE state in the same manner that they are predicted in ARM or Thumb state. In addition, the handler base branch instructions, HB[L][P], are also predicted using the same branch prediction hardware used for direct branch and branch link, B and BL instructions, respectively. Because the ThumbEE instruction set uses R9 as the base register rather than R13 as a stack pointer, LDR and STR instructions that read or write to the PC are written onto the return stack to aid in the prediction of these indirect branches. The usage model of the return stack in ThumbEE state, using R9 as the stack pointer, is identical to the usage model in ARM and Thumb state, using R13 as the stack pointer. Because the processor is statically scheduled, it schedules conditional instructions on the basis that they pass their condition codes. This means multi-cycle instructions such as LDM and STM instructions can still complete all their iterations even if they fail their condition codes. An additional point about conditional instructions is that the destination register of the instruction is treated as an additional source operand. This is done so the old value can be forwarded in the case when the instruction fails the condition codes. This additional source operand is required in the E2 stage of the machine. ARM DDI 0344K Copyright © 2006-2010 ARM Limited. All rights reserved. 16-16 ID060510 Non-Confidential
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Copyright © 2006-2010 ARM Limited.
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Web Address http://www.arm.com ARM
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Contents 2.14 The program status re
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Contents 16.6 Instruction-specific
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List of Tables Table 3-16 Debug Fea
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List of Tables Table 3-136 Secure o
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List of Tables Table 12-59 Values t
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List of Figures Cortex-A8 Technical
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List of Figures Figure 3-77 BTB arr
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List of Figures Figure 15-16 CTI Ch
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About this manual Product revision
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old Highlights interface elements,
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Feedback Feedback on the product Fe
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1.1 About the processor Introductio
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1.3 Components of the processor L1
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1.3.6 NEON 1.3.7 ETM The NEON unit
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1.5 Debug Introduction The processo
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1.7 Configurable options Table 1-1
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Introduction • The various data a
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1.9.6 r2p0-r2p1 1.9.7 r2p1-r2p2 1.9
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Chapter 2 Programmers Model This ch
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2.2 Thumb-2 instruction set Program
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Bits Field Function Programmers Mod
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2.4 Jazelle Extension 2.4.1 Jazelle
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2.5 Security Extensions architectur
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2.6 Advanced SIMD architecture Prog
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2.8 Processor operating states 2.8.
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2.10 Memory formats 2.10.1 Byte-inv
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2.12 Operating modes Programmers Mo
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System and User r0 r1 r2 r3 r4 r5 r
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2.14 The program status registers 2
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2.14.5 The GE[3:0] bits Programmers
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Mode bits Programmers Model M[4:0]
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2.15 Exceptions 2.15.1 Exception en
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2.15.5 Interrupt request 2.15.6 Abo
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This restores both the PC and the C
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2.15.13 Exception priorities Progra
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2.17 Hardware consideration for Sec
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SECMONOUT[78] instruction caches at
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Chapter 3 System Control Coprocesso
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System Control Coprocessor Register
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3.1.3 MMU control and configuration
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3.2 System control coprocessor regi
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CRn Op1 CRm Op2 Register or operati
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3.2.2 c0, Main ID Register System C
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3.2.4 c0, TCM Type Register 3.2.5 c
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3.2.7 c0, Processor Feature Registe
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• accessible in privileged modes
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System Control Coprocessor Table 3-
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Bits Field Function [11:8] L1 Harva
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Bits Field Function [11:8] Harvard
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31 28 27 24 23 20 19 16 15 12 11 8
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Table 3-30 shows the results of att
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System Control Coprocessor 31 28 27
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Table 3-36 shows the results of att
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• accessible in privileged modes
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CSSR Size 3.2.24 c0, Cache Size Sel
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System Control Coprocessor 31 30 29
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MCR p15, 0, , c1, c0, 0 ; Write Con
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Bits Field [19] Clock stop request
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Bits Field Security State NS S Tabl
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3.2.28 c1, Secure Configuration Reg
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AW EA Function Table 3-55 shows the
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3.2.32 c2, Translation Table Base R
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System Control Coprocessor Figure 3
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Bits Field Function 3.2.35 c5, Data
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3.2.36 c5, Instruction Fault Status
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3.2.38 c6, Data Fault Address Regis
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System Control Coprocessor Note •
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System Control Coprocessor Figure 3
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3.2.41 c8, TLB operations The data
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Figure 3-38 shows the bit arrangeme
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EN b 3.2.44 c9, Count Enable Clear
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EN b 3.2.46 c9, Software Increment
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EN b 3.2.48 c9, Cycle Count Registe
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EN b Table 3-96 shows the results o
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Value Description 0x44 Any cacheabl
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DBGEN || NIDEN 3.2.51 c9, User Enab
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EN 3.2.53 c9, Interrupt Enable Clea
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Figure 3-48 shows the bit arrangeme
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3.2.55 c9, L2 Cache Auxiliary Contr
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Bits Field Function [8:6] Tag RAM l
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TL bit value 3.2.57 c10, TLB preloa
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The PLE Identification and Status R
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3.2.62 c11, PLE enable commands U b
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Bits Field Function System Control
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U bit PLE bit Table 3-129 shows the
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U bit PLE bit System Control Coproc
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3.2.68 c12, Secure or Nonsecure Vec
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3.2.70 c12, Interrupt Status Regist
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The FCSE PID Register is: • a rea
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TLB CAM read/write TLB ATTR read/wr
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MCR p15 0, , c15, c3, 4 ; I-L1 TLB
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31 27 26 22 21 0 Reserved L1 Data 0
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System Control Coprocessor The L1 H
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3.2.78 c15, L1 data array operation
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Instruction L1 Data 0 register Inst
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Parity/ECC RAM read/write Data RAM
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3.2.82 c15, L2 parity/ECC array ope
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3.2.84 c15, L2 data array operation
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4.1 About unaligned and mixed-endia
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Unaligned Data and Mixed-endian Dat
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Chapter 5 Program Flow Prediction T
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5.2 Predicted instructions Program
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Program Flow Prediction Because ret
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5.4 Guidelines for optimal performa
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5.6 Operating system and predictor
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6.1 About the MMU Memory Management
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6.3 16MB supersection support Memor
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6.5 External aborts 6.5.1 External
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6.7 MMU software-accessible registe
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7.1 About the L1 memory system Leve
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7.2.6 Instruction cache maintenance
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L1 inner policy a L2 outer policy N
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7.5 Data cache features 7.5.1 Data
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7.7 Hardware support for virtual al
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Chapter 8 Level 2 Memory System Thi
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8.2 Cache organization 8.2.1 L2 cac
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8.3 Enabling and disabling the L2 c
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Level 2 Memory System Note It is en
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Level 2 Memory System Note You must
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Lock address : LockAddr Lock free :
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8.7 Parity and error correction cod
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9.1 About the external memory inter
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Integer data and CP14 writes Noncac
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9.4 AXI data read/write transaction
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Noncacheable, or strongly ordered,
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Noncacheable store word Noncacheabl
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LA Last Access External Memory Inte
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10.1 Clock domains 10.1.1 AXI clock
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10.2 Reset domains 10.2.1 Power-on
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REFCLK (PLL input) nPORESET ARESETn
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10.3 Power control 10.3.1 Dynamic p
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Clock, Reset, and Power Control the
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ATB APB I/O clamp I/O clamp L/S = L
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ATB APB I/O clamp I/O clamp LS = Le
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Clock, Reset, and Power Control 3.
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Powering up the debug and ETM domai
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7. Perform a normal software reset
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Clock, Reset, and Power Control 5.
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Chapter 11 Design for Test This cha
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In L1 MBIST Instruction Register Fi
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Note Do not test the CAMBIST arrays
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• number of rows of the L2 data,
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Design for Test Not all row setting
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In Design for Test Figure 11-4 show
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Design for Test When testing the ta
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CLK ARESETn MBISTMODE MBISTSHIFT MB
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End-of-test datalog retrieval Desig
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Pattern N RWRXMARCH 8N Row-fast Sta
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4. rscan array, data_seed = invert.
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3. R_, W, R, decr. 4. rscan data fr
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• the data after pass 1 of XADDRB
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(1 + (2 17)) 2 17 = 4,587,520 cycle
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processor input ports WEXTEST WINTE
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Design for Test toggling during shi
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12.1 Debug systems 12.1.1 Debug hos
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12.2.3 Security extensions and debu
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Instruction Mnemonic Description 12
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12.3.6 Power domains and debug 12.3
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Table 12-5 shows the APB interface
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12.4 Debug register descriptions Te
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MRC p14, 0, , c0, c0, 0 ; Read Debu
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31 30 29 28 27 26 25 24 23 22 21 20
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Bits Field Function [21:20] DTR acc
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Bits Field Function To access the D
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12.4.7 Watchpoint Fault Address Reg
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Bits Access Normal address [2] RW V
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12.4.12 Debug Run Control Register
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Table 12-23 shows how the bit value
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BVR[22:20] Meaning b011 The corresp
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Bits Field Function [15:14] Secure
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12.4.18 Operating System Lock Statu
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Debug • The sequence can be aband
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12.5 Management registers Offset Th
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Offset Register number Mnemonic Fun
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Bits Field Function [5] nDMAIRQ nDM
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12.5.7 Claim Tag Clear Register 12.
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12.5.10 Authentication Status Regis
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Table 12-45 shows fields that are i
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12.6 Debug events 12.6.1 Software d
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12.6.5 Watchpoint debug events If a
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Table 12-53 shows the values in the
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12.8 Debug state 12.8.1 Entering de
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12.8.4 Writing to the CPSR in debug
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Mode SCR[0] For CP15 instructions,
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12.8.9 Leaving debug state Imprecis
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12.9.3 Cache usage profiling Debug
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Note DBGPWRDWNREQ must be tied LOW
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If software running on the processo
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Rules for accessing the DCC At the
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} While the processor is running, i
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Debug Table 12-59 Values to write t
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12.11.4 Debug state entry Example 1
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} // Step 1. Update the CPSR value
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Writing the CPSR in debug state Exa
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Debug Example 12-21 Reading a word
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} // Step 9. Check for aborts. abor
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12.12 Debugging systems with energy
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MOV r0, r4 POP {r4, pc} Example 12-
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Chapter 13 NEON and VFP Programmers
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13.2 General-purpose registers 13.2
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13.3 Short vectors 13.3.1 About reg
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13.3.2 Operations using register ba
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NEON and VFP Programmers Model The
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Note All hardware ID information is
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Bits Field Function [12:8] - Reserv
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NEON and VFP Programmers Model Tabl
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13.6 Compliance with the IEEE 754 s
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Underflow NEON and VFP Programmers
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14.1 About the ETM 14.1.1 ETM featu
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14.1.3 NEON Bridge and bus matrix A
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14.3 ETM register summary The ETM r
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Bits Field Function [11:8] Major ET
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14.4.4 Peripheral Identification Re
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See the ETM Architecture Specificat
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Embedded Trace Macrocell Table 14-1
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Page 457 and 458: 14.5.3 Enabling events 14.5.4 Addre
Page 459 and 460: 14.7 Context ID tracing Embedded Tr
Page 461 and 462: 14.9 Idle state control Embedded Tr
Page 463 and 464: Embedded Trace Macrocell Table 14-1
Page 465 and 466: Chapter 15 Cross Trigger Interface
Page 467 and 468: CTICHIN[0] CTICHIN[1] CTICHIN[2] CT
Page 469 and 470: 15.2 Trigger inputs and outputs Tri
Page 471 and 472: 15.3 Connecting asynchronous channe
Page 473 and 474: 15.5 CTI register summary Address o
Page 475 and 476: 15.6 CTI register descriptions This
Page 477 and 478: 15.6.4 CTI Application Trigger Clea
Page 479 and 480: Table 15-10 shows how the bit value
Page 481 and 482: 15.6.12 ASIC Control Register, ASIC
Page 483 and 484: 15.7 CTI Integration Test Registers
Page 485 and 486: 15.7.4 ITTRIGOUTACK, 0xEF0 15.7.5 I
Page 487 and 488: Cross Trigger Interface Table 15-26
Page 489 and 490: 15.8.3 Device Type Identifier, 0xFC
Page 491 and 492: Cross Trigger Interface Table 15-31
Page 493 and 494: 16.1 About instruction cycle timing
Page 495 and 496: Instruction Cycle Timing Example 16
Page 497 and 498: Table 16-4 shows the operation of m
Page 499 and 500: Table 16-9 shows the operation of l
Page 501 and 502: d. See Load/store instructions on p
Page 503 and 504: Instruction Cycle Timing Table 16-1
Page 505: 16.4 Other pipeline-dependent laten
Page 509 and 510: 16.6 Instruction-specific schedulin
Page 511 and 512: Instruction Cycle Timing VNEG Dd,Dm
Page 513 and 514: VMLA a VMLS a VMLAa VMLSa VQDMLAa V
Page 515 and 516: VSLI VSRI 16.6.5 Advanced SIMD floa
Page 517 and 518: 16.6.6 Advanced SIMD byte permute i
Page 519 and 520: Instruction Table 16-23 shows the o
Page 521 and 522: Instruction VST3 3-reg (unaligned)
Page 523 and 524: Instruction VLD3 3-reg (unaligned)
Page 525 and 526: Instruction Single precision cycles
Page 527 and 528: • FMACS, FNMACS • FMSCS, FNMSCS
Page 529 and 530: is dual issued with previous instru
Page 531 and 532: 17.1 About setup and hold times AC
Page 533 and 534: 17.2 AXI interface Table 17-2 shows
Page 535 and 536: 17.3 ATB and CTI interfaces Table 1
Page 537 and 538: AC Characteristics Table 17-4 Timin
Page 539 and 540: 17.6 L2 preload interface AC Charac
Page 541 and 542: 17.8 Miscellaneous signals AC Chara
Page 543 and 544: A.1 AXI interface Signal Descriptio
Page 545 and 546: A.3 MBIST and DFT interface A.3.1 M
Page 547 and 548: A.4 Preload engine interface Table
Page 549 and 550: A.6 Miscellaneous signals Table A-7
Page 551 and 552: Signal I/O Reset Description CFGNMF
Page 553 and 554: Signal I/O Reset Description DBGNOP
Page 555 and 556: Appendix B Instruction Mnemonics Th
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Instruction Mnemonics Table B-1 Adv
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Appendix C Revisions This appendix
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Revisions Added text to clarify des
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Glossary This glossary describes so
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Glossary Automatic Test Pattern Gen
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Big-endian memory Memory in which:
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Conditional execution Glossary incl
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Glossary Embedded Trace Macrocell (
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Illegal instruction An instruction
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Glossary NaN Not a number. A symbol
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Glossary Significand The component
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Glossary Watchpoint A watchpoint is
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