Working with ETM/SWO on high performance Cortex-M7 devices

David Källberg, Field Application Engineer

Agenda • Arm Cortex-M7

– Architecture – Debug features

• Achieve max SWO/ETM performance • Demo SWO/ETM on STM32H7

Arm Cortex-M7

Arm Cortex-M7

Arm Cortex-M7 • High performance core

• More power efficient then Arm Cortex-M4

• 6-stage pipeline

• Optional SP/DP FPU

• Complete hardware debug solution – Coresight with ETMv4, ITM and SWO

DWT

CPU statistics

FPB 8 breakpoints

DAP

JTAG

Live core access

I-jet

Interrupt trace SWD/SWO

ITM Instrumentation Trace

ETM trigger

ETB instruction trace

ETB Embedded Trace Buffer

ETM Embedded Trace Macrocell

ETMv4

instruction trace

Trace port

4 watchpoints

PC sampler ITM Software trace 32 channels

Time stamping

Cortex-M7 Coresight overview

6 SWD

Achieve max SWO/ETM performance

Performance – the challenge • Cortex-M7 devices runs very fast

– i.MX RT runs @ 600 MHz • Performance limited by:

– CPU I/O performance – PCB, connectors and cables – Debug probe

SWO - features • Sampled instruction trace • Data access log

– DWT has 4 watchpoints • Interrupt log • ITM events

– Non-intrusive printf style messages • And more...

SWO - performance

Example – STM32H7 – CPU clk 400 MHz – PLL1VCO = 800 MHz – DIRR = 3 – SWO clocked by 800/3 – SWO prescaler – Manchester mode (/2)

Setup – Manchester mode – 266.66 MHz clock – With I-jet:

266/4/2 = 33 MHz – With I-jet Trace

266/2/2 = 66 MHz

ETM - features • Complete instruction trace • Travel back in time

– Millions of instructions • Profiling • Code coverage • And more...

ETM - performance Example – STM32H7

– CPU clk 400 MHz – PLL1VCO = 800 MHz – Board spec

TRACECLK = 50 MHz

Setup – I-jet Trace – MIPI 20 connector – CLK = 800/3/2 = 133M – ETM capture success

Demo ETM/SWO on STM32H7

• SuperSpeed USB 3.0 interface (5 Gbps) • Fully compatible with USB 2.0 (480 Mbps) • No power supply required, powered entirely by the USB port • Target power of up to 600mA can be supplied from I-jet Trace

with overload protection • Automatic core recognition • JTAG, SWD, target power consumption measuring

I-jet Trace for ARM Cortex-A/R/M

Trace features • Trace memory size up to 256 Mbyte • Up to 16-bit wide trace data collection • Up to 350MHz ETM trace clock • 64-bit timestamp with CPU cycle accuracy for timing analysis • Automatic alignment of parallel trace data skew on individual bits to compensate for PCB layout

and signal integrity problems • Automatic trace data and clock voltage threshold adjustments to get the most reliable capture with

noisy or un-terminated target boards • Support for trace logic levels from 1.2 V to 5V

Summary • Cortex-M7 brings high performance

• SWO and ETM gives possibilities

• Requires good debug performance

• I-jet and I-jet Trace enables high performance debugging of Cortex-M7

• Get scanned to have this presentation emailed to you.

• Visit IAR Demo Space to get a demo of our technology.

Want to learn more?

Thank you for your attention!