STM32W108HB datasheet(155/179 Pages) STMICROELECTRONICS

155 / 179 page

STM32W108CB, STM32W108HB

Debug support

Doc ID 16252 Rev 2

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Debug support

The STM32W108 includes a standard Serial Wire and JTAG (SWJ) Interface. The SWJ is

the primary debug and programming interface of the STM32W108. The SWJ gives debug

tools access to the internal buses of the STM32W108, and allows for non-intrusive memory

and register access as well as CPU halt-step style debugging. Therefore, any design

implementing the STM32W108 should make the SWJ signals readily available.

Serial Wire is an ARM® standard, bi-directional, two-wire protocol designed to replace

JTAG, and provides all the normal JTAG debug and test functionality. JTAG is a standard

five-wire protocol providing debug and test functionality. In addition, the two Serial Wire

signals (SWDIO and SWCLK) are overlaid on two of the JTAG signals (JTMS and JTCK).

This keeps the design compact and allows debug tools to switch between Serial Wire and

JTAG as needed, without changing pin connections.

While Serial Wire and JTAG offer the same debug and test functionality, ST recommends

Serial Wire. Serial Wire uses only two pins instead of five, and offers a simple

communication protocol, high performance data rates, low power, built-in error detection,

and protection from glitches.

The ARM® CoreSight Debug Access Port (DAP) comprises the Serial Wire and JTAG

Interface (SWJ).The DAP includes two primary components: a debug port (the SWJ-DP)

and an access port (the AHB-AP). The SWJ-DP provides external debug access, while the

AHB-AP provides internal bus access. An external debug tool connected to the

STM32W108's debug pins communicates with the SWJ-DP. The SWJ-DP then

communicates with the AHB-AP. Finally, the AHB-AP communicates on the internal bus.

Figure 48.

SWJ block diagram

Serial Wire and JTAG share five pins:

●

JRST

●

JTDO

●

JTDI

●

SWDIO/JTMS

●

SWCLK/JTCK

Since these pins can be repurposed, refer to Section 2: Pinout and pin description on

page 17 and Section 6: General-purpose input/outputs on page 46 for complete pin

descriptions and configurations.

STM32W108HB Datasheet(PDF) 155 Page - STMicroelectronics

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