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RM0016

Single wire interface module (SWIM) and debug module (DM)

 

 

5Single wire interface module (SWIM) and debug module (DM)

5.1Introduction

In-circuit debugging mode or in-circuit programming mode are managed through a single wire hardware interface featuring ultrafast memory programming. Coupled with an in-circuit debugging module, it also offers a non-intrusive emulation mode, making the in-circuit debugger extremely powerful, close in performance to a full-featured emulator.

5.2Main features

Based on an asynchronous, high sink (8 mA), open-drain, bidirectional communication.

Allows reading or writing any part of memory space.

Access to CPU registers (A, X, Y, CC, SP). They are memory mapped for read or write access.

Non intrusive read/write on the fly to the RAM and peripheral registers.

Device reset capability with status flag in the Reset status register (RST_SR).

Clock speed selectable in the SWIM clock control register (CLK_SWIMCCR).

SWIM pin can be used as a standard I/O with some restrictions if you also want to use it for debug. The most secure way is to provide on the PCB a strap option.

Figure 12. SWIM pin connection

I/O for application

 

 

 

MCU

 

 

 

 

 

SWIM/PA0

SWIM interface for tools

Jumper selection for debug purposes

5.3SWIM modes

After a power-on reset, the SWIM is reset and enters OFF mode.

1.OFF: Default state after power-on reset. The SWIM pin cannot be used by the application as an I/O.

2.I/O: This state is entered by software writing to the SWD bit in the Global configuration register (CFG_GCR). In this state, the SWIM pin can be used by the application as a standard I/O pin. In case of a reset, the SWIM goes back to OFF mode.

3.SWIM: This state is entered when a specific sequence is performed on the SWIM pin. In this state, the SWIM pin is used by the host tool to control the STM8 with 3 commands (SRST system reset, ROTF read on the fly, WOTF write on the fly).

Note:

Refer to the STM8 SWIM communication Protocol and Debug Module User Manual for a

 

description of the SWIM and Debug module (DM) registers.

Doc ID 14587 Rev 9

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