Configure Swo Output After Device Reset - Segger J-Link User Manual

106
Syntax
-swofreq <SWOFreq>
Example
-swofreq 6000
3.8.3

Configure SWO output after device reset

In some situations it might happen that the target application is reset and it is desired to log
the SWO output of the target after reset during the booting process. For such situations, the
target application itself needs to initialize the CPU for SWO output, since the SWO Viewer
is not restarted but continuously running.
Example code for enabling SWO out of the target application
#define ITM_ENA
#define ITM_TPR
#define ITM_TCR
#define ITM_LSR
#define DHCSR
#define DEMCR
#define TPIU_ACPR
#define TPIU_SPPR
#define DWT_CTRL
#define FFCR
U32 _ITMPort
U32 TargetDiv = 1;
static void _EnableSWO() {
U32 StimulusRegs;
//
// Enable access to SWO registers
//
DEMCR |= (1
ITM_LSR = 0xC5ACCE55;
//
// Initially disable ITM and stimulus port
// To make sure that nothing is transferred via SWO
// when changing the SWO prescaler etc.
//
StimulusRegs = ITM_ENA;
StimulusRegs &=
ITM_ENA = StimulusRegs;
ITM_TCR = 0;
//
// Initialize SWO (prescaler, etc.)
//
TPIU_SPPR = 0x00000002;
TPIU_ACPR = TargetDiv - 1;
ITM_TPR = 0x00000000;
DWT_CTRL = 0x400003FE;
FFCR = 0x00000100;
//
// Enable ITM and stimulus port
//
ITM_TCR = 0x1000D;
ITM_ENA = StimulusRegs |
J-Link / J-Trace (UM08001)
(*(volatile unsigned
(*(volatile unsigned
(*(volatile unsigned
(*(volatile unsigned
(*(volatile unsigned
(*(volatile unsigned
(*(volatile unsigned
(*(volatile unsigned
(*(volatile unsigned
(*(volatile unsigned
= 0; // The stimulus port from which SWO data is received
// and displayed.
// Has to be calculated according to
// the CPU speed and the output baud rate
<< 24);
~(1 << _ITMPort);
// Disable ITM stimulus port
// Disable ITM
// Select NRZ mode
// Example: 72/48 = 1,5 MHz
// Enable ITM
(1 << _ITMPort);
CHAPTER 3
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int*)0xE0000E40)
int*)0xE0000E80)
int*)0xE0000FB0)
int*)0xE000EDF0)
int*)0xE000EDFC)
int*)0xE0040010)
int*)0xE00400F0)
int*)0xE0001000)
int*)0xE0040304)
// Enable ITM stimulus port
© 2004-2017 SEGGER Microcontroller GmbH & Co. KG
J-Link SWO Viewer
// ITM Enable
// Trace Privilege
// Register
// ITM Trace Control Reg.
// ITM Lock Status
// Register
// Debug register
// Debug register
// Async Clock
// prescaler register
// Selected Pin Protocol
// Register
// DWT Control Register
// Formatter and flush
// Control Register