Universität Dortmund. ARM Cortex-M3 Buses

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Richard Briggs
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1 ARM Cortex-M3 Buses

2 Modulo 2 No change in class organization Thursday aftenoon (17-19) Lectures (Rossi) Aprile Giugno (Mod 2) room 1.3 Friday afternoon (14-18) (Benatti): LAB2 Content natural prosecution of contents started with Prof. Benini+ Busses, memories, DMA I/O interfaces and DAC/ADC Power management in embedded system Wireless protocols Sensors & actuators Compilation, RTOS Advanced Architectures for IoT A unique exam for the 2 modules (lab report + oral discussion): I appello 11 Giugno 2018 ore 13:00 Aula T.B.D. II appello 16 Luglio 2018 ore 13:30 Aula T.B.D. Contacts: davide.rossi@unibo.it News, material and updates on the Website:

3 Processor vs. MCU Focus today

4 Core Architecture Diagram

5 Embedded Processor I/O RISC-based embedded processors communicate with external hardware using two simple instructions: Load Operation: Copies a word of data from a specific address to a local register Store Operation: Copies a word of data from a local register to a specific address

6 Memory map Statically defined memory map (faster addr decoding) 4GB of address psace

7 Embedded Processor I/O EXT MEM MEMORY Blocks decode addresses to see if they are the targets... Software sets up the register with the address and data... Data transferred between register and hardware

8 Accessing memory locations from C Memory has an address and value Can equate a pointer to desired address Can set/get de-referenced value to change memory #define SYSREG_SOFT_RST_CR 0xE uint32_t *reg = (uint32_t *)(SYSREG_SOFT_RST_CR); main () { *reg = 0x ; // Writing 0x to address 0xE } 8

9 What happens when this instruction executes? #include <stdio.h> #include <inttypes.h> #define REG_FOO 0x main () { uint32_t *reg = (uint32_t *)(REG_FOO); *reg += 3; } printf( 0x%x\n, *reg); // Prints out new value 9

10 *reg += 3 is turned into a ld, add, str sequence Load instruction A bus read operation commences The CPU drives the address reg onto the address bus The CPU indicated a read operation is in process (e.g. R/W#) Some handshaking occurs The target drives the contents of reg onto the data lines The contents of reg is loaded into a CPU register (e.g. r0) Add instruction An immediate add (e.g. add r0, #3) adds three to this value Store instruction A bus write operation commences The CPU drives the address reg onto the address bus The CPU indicated a write operation is in process (e.g. R/W#) Some handshaking occurs The CPU drives the contents of r0 onto the data lines The target stores the data value into address reg 10

11 Some useful C keywords const Makes variable value or pointer parameter unmodifiable const foo = 32; register Tells compiler to locate variables in a CPU register if possible register int x; static Preserve variable value after its scope ends Does not go on the stack static int x; volatile Opposite of const Can be changed in the background volatile int I; 11

APB2 (max 84MHz) ARM 32-bit multi-ahb bus matrix Arbiter (max 168MHz) Flash I/F STM32F4xx Block Diagram Cortex-M4 w/ FPU, MPU and ETM Memory Up to 1MB Flash memory

AES 256-bit, SHA-1 hash, RNG. Enhanced peripherals USB OTG Full speed ADC: 0.416µs conversion/2.4msps, up to 7.

0 32-bit RTC with calendar 4KB backup SRAM in VBAT domain 2 x 32bit and 8 x 16bit Timers high speed USART up to 10.5Mb/s high speed SPI up to 37.

Channels Clock Control 51/82/114/140 I/Os 2x6x 16-bit PWM Synchronized AC Timer 3 x 16bit Timer Up to 16 Ext.

0 OTG FS/HS Ethernet MAC 10/100, IEEE1588 Bridge 512kB- 1MB Flash Memory 128KB SRAM External Memory Interface APB1 (max 42MHz) 5x 16-bit Timer 2x 32-bit Timer 2x

12 APB2 (max 84MHz) ARM 32-bit multi-ahb bus matrix Arbiter (max 168MHz) Flash I/F STM32F4xx Block Diagram Cortex-M4 w/ FPU, MPU and ETM Memory Up to 1MB Flash memory 192KB RAM (including 64KB CCM data RAM FSMC up to 60MHz New application specific peripherals USB OTG HS w/ ULPI interface Camera interface HW Encryption**: DES, 3DES, AES 256-bit, SHA-1 hash, RNG. Enhanced peripherals USB OTG Full speed ADC: 0.416µs conversion/2.4msps, up to 7.2Msps in interleaved triple mode ADC/DAC working down to 1.8V 2 Dedicated PLL for I S precision Ethernet w/ HW IEEE1588 v bit RTC with calendar 4KB backup SRAM in VBAT domain 2 x 32bit and 8 x 16bit Timers high speed USART up to 10.5Mb/s high speed SPI up to 37.5Mb/s RDP (JTAG fuse) More I/Os in UFBGA 176 package 64KB CCM data RAM CORTEX-M4 CPU + FPU + MPU 168 MHz JTAG/SW Debug ETM Nested vect IT Ctrl 1 x Systic Timer DMA 16 Channels Clock Control 51/82/114/140 I/Os 2x6x 16-bit PWM Synchronized AC Timer 3 x 16bit Timer Up to 16 Ext. ITs 1 x SPI 2 x USART/LIN D-bus I-bus S-bus AHB1 (max 168MHz) Bridge AHB2 (max 168MHz) USB 2.0 OTG FS/HS Ethernet MAC 10/100, IEEE1588 Bridge 512kB- 1MB Flash Memory 128KB SRAM External Memory Interface APB1 (max 42MHz) 5x 16-bit Timer 2x 32-bit Timer 2x Watchdog (independent& window) 1x SDIO 3x 12-bit ADC 24 channels / 2Msps Temp Sensor HS requires an external PHY connected to ULPI interface, ** Encryption is only available on STM32F415 and STM32F417 Encryption** Camera Interface USB 2.0 OTG FS Power Supply Reg 1.2V POR/PDR/PVD XTAL oscillators 32KHz + 8~25MHz Int. RC oscillators 32KHz + 16MHz PLL RTC / AWU 4KB backup RAM 2x DAC + 2 Timers 2x CAN 2.0B 2 x SPI / I 2 S 4x USART/LIN 3x I 2 C 4

13 On-Chip Buses

14 Why have so many busses? Many designs considerations Master vs Slave Internal vs External Bridged vs Flat Memory vs Peripheral High-speed vs low-speed Serial vs Parallel Single master vs multi master Single layer vs multi layer Multiplexed A/D vs demultiplexed A/D Discussion: what are some of the tradeoffs? 14

15 Advanced Microcontroller Bus Architecture (AMBA) Advanced High-performance - Bus (AHB) Advanced Peripheral Bus (APB) AHB High performance Pipelined operation Burst transfers Multiple bus masters Split transactions APB Low power Latched address/control Simple interface Suitable of many peripherals

16 Key to timing diagram conventions Timing diagrams Clock Stable values Transitions High-impedance Signal conventions Lower case n denote active low (e.g. RESETn) Prefix H denotes AHB Prefix P denotes APB 16

17 APB is simpler interface than AHB Low-cost Low-power Low-complexity Low-bandwidth Non pipelined Ideal for peripherals 17

18 APB signal definitions PCLK: the bus clock source (rising-edge triggered) PRESETn: the bus (and typically system) reset signal (active low) PADDR: the APB address bus (can be up to 32-bits wide) PSELx: the select line for each slave device PENABLE: indicates the 2 nd and subsequent cycles of an APB xfer PWRITE: indicates transfer direction (Write=H, Read=L) PWDATA: the write data bus (can be up to 32-bits wide) PREADY: used to extend a transfer PRDATA: the read data bus (can be up to 32-bits wide) PSLVERR: indicates a transfer error (OKAY=L, ERROR=H) 18

19 APB state machine IDLE Default APB state SETUP When transfer required PSELx is asserted Only one cycle ACCESS PENABLE is asserted Addr, write, select, and write data remain stable Stay if PREADY = L Goto IDLE if PREADY = H and no more data Goto SETUP is PREADY = H and more data pending 19

20 A write transfer with no wait states Setup phase begins with this rising edge Setup Phase Access Phase 20

21 A read transfer with no wait states Setup phase begins with this rising edge Setup Phase Access Phase

22 A read transfer with wait states Setup phase begins with this rising edge Setup Phase Wait State Wait State Access Phase 22

23 AHB-Lite Supports single bus master and provides highbandwidth operation Burst transfers Single clock-edge operation Non-tri-state implementation Configurable bus width 23

24 AHB-Lite bus master/slave interface Global signals HCLK HRESETn Master out/slave in HADDR (address) HWDATA (write data) Control HWRITE HSIZE HBURST HPROT HTRANS HMASTLOCK Slave out/master in HRDATA (read data) HREADY HRESP 24

25 Global signals AHB-Lite signal definitions HCLK: the bus clock source (rising-edge triggered) HRESETn: the bus (and system) reset signal (active low) Master out/slave in HADDR[31:0]: the 32-bit system address bus HWDATA[31:0]: the system write data bus Control HWRITE: indicates transfer direction (Write=1, Read=0) HSIZE[2:0]: indicates size of transfer (byte, halfword, or word) HBURST[2:0]: indicates single or burst transfer (1, 4, 8, 16 beats) HPROT[3:0]: provides protection information (e.g. I or D; user or handler)* HTRANS: indicates current transfer type (e.g. idle, busy, nonseq, seq)* HMASTLOCK: indicates a locked (atomic) transfer sequence* Slave out/master in HRDATA[31:0]: the slave read data bus HREADY: indicates previous transfer is complete HRESP: the transfer response (OKAY=0, ERROR=1) 25

26 Basic read and write transfers with no wait states Pipelined Address & Data Transfer 26

27 Universität Wait Dortmund states extend the address phase of next transfer Address stage of the next transfer is also extended One wait state added by slave by asserting HREADY low 27

28 Read transfer with two wait states Two wait states added by slave by asserting HREADY low Valid data produced 28

29 Write transfer with one wait state One wait state added by slave by asserting HREADY low Valid data held stable 29

30 Transfers can be of four types (HTRANS[1:0]) IDLE (b00) No data transfer is required Slave must OKAY w/o waiting Slave must ignore IDLE BUSY (b01) Insert idle cycles in a burst Burst will continue afterward Address/control reflects next transfer in burst Slave must OKAY w/o waiting Slave must ignore BUSY NONSEQ (b10) Indicates single transfer or first transfer of a burst Address/control unrelated to prior transfers SEQ (b11) Remaining transfers in a burst Addr = prior addr + transfer size 30

31 A Universität four Dortmund beat burst with master busy and slave wait Master busy indicated by HTRANS[1:0] One wait state added by slave by asserting HREADY low

32 Controlling the size (width) of a transfer HSIZE[2:0] encodes the size Cannot exceed the data bus width (e.g. 32-bits) HSIZE + HBURST determines wrapping boundary for wrapping bursts HSIZE must remain constant throughout a burst transfer 32

33 Universität Controlling Dortmund the burst beats (length) of a transfer Burst of 1, 4, 8, 16, and undef HBURST[2:0] encodes the type Incremental burst Wrapping bursts 4 beats x 4-byte words wrapping Wraps at 16 byte boundary E.g. 0x34, 0x38, 0x3c, 0x30, Bursts must not cross 1KB address boundaries 33

34 A four beat incrementing burst (INCR4) 34

35 A four beat wrapping burst (WRAP4) 35

36 An eight beat wrapping burst (WRAP8) 36

37 Universität An Dortmund eight beat incrementing burst (INCR8) using half-word transfers 37

38 Universität An Dortmund undefined length incrementing burst (INCR) 38

39 Multi-master AHB-Lite requires a multi-layer interconnect AHB-Lite is single-master Multi-master operation Must isolate masters Each master assigned to layer Interconnect arbitrates slave accesses Full crossbar switch often unneeded Slaves 1, 2, 3 are shared Slaves 4, 5 are local to Master 1 39

EECS 373. Design of Microprocessor-Based Systems. Prabal Dutta University of Michigan. Announcements. Homework #2 Where was I last week?

EECS 373. Design of Microprocessor-Based Systems. Prabal Dutta University of Michigan. Announcements. Homework #2 Where was I last week? Announcements EECS 373 Homework #2 Where was I last week? Design of Microprocessor-Based Systems VLCS 14 MobiCom 14 HotWireless 14 Prabal Dutta University of Michigan Lecture 5: Memory and Peripheral Busses