Freescale Semiconductor, Inc

FRDM-KL46Z

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5.1.2 Serial and Debug Adapter (OpenSDA)

OpenSDA is an open-standard serial and debug adapter. It bridges serial and debug communications between a

USB host and an embedded target processor as shown in Figure 4. The hardware circuit is based on a Freescale

Kinetis K20 family microcontroller (MCU) with 128 KB of embedded flash and an integrated USB controller.

OpenSDA features a mass storage device (MSD) bootloader, which provides a quick and easy mechanism for

loading different OpenSDA Applications such as flash programmers, run-control debug interfaces, serial-to-USB

converters, and more. Refer to the OpenSDA User’s Guide for more details.

Figure 4. OpenSDA High-Level Block Diagram

OpenSDA is managed by a Kinetis K20 MCU built on the ARM® Cortex™-M4 core. The OpenSDA circuit includes a

status LED (D8) and a pushbutton (SW2). The pushbutton asserts the Reset signal to the KL46 target MCU. It can

also be used to place the OpenSDA circuit into Bootloader mode. SPI and GPIO signals provide an interface to

either the SWD debug port of the K20. Additionally, signal connections are available to implement a UART serial

channel. The OpenSDA circuit receives power when the USB connector J13 is plugged into a USB host.

Debug Interface

Signals with SPI and GPIO capability are used to connect directly to the SWD of the KL46. These signals are also

brought out to a standard 10-pin (0.05”) Cortex Debug connector (J11). It is possible to isolate the KL46 MCU

from the OpenSDA circuit and use J11 to connect to an off-board MCU. To accomplish this, cut the trace on the

bottom side of the PCB that connects J18 pin 2 to J11 pin 2. This will disconnect the SWD_CLK pin to the KL46 so

that it will not interfere with the communications to an off-board MCU connected to J11.