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Operation Mode Control--Jones Chen

Jones Chen

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Author: Jones Chen in Texas Instruments

1）JTAG pin

2）TRST

Do not use pull-up resistors on TRST: it has an internal pull-down device.

In a low-noise environment, TRST can be left floating.

In a high-noise environment, an additional pull-down resistor may be needed. (The size of this resistor should be based on electrical current considerations.)

3）Operations Mode Status Latched

The state of the TRST, EMU0, and EMU1 signals at device power up determine the operating mode of the device. The operating mode takes effect as soon as the device has sufficient power to operate. Should the TRST signal rise, the EMU0 and EMU1 signals are sampled on its rising edge and the\at operating mode is latched.

4）Test Program

A test program has been programmed, the program has been burn to flash in advance. The program toggles the GPIO34 which connected to LED3 to let the LED blink.

5）EMU0 and EMU1 Circuits:

6）XRST Circuit:

7）Experiment Description:

Emulator is disabled, so the TRST=0 when power on

Once power on, the four signals TRST XRST EMU0 EMU1 are monitored from the oscillograph.

1） The yellow line is the TRST signal

2） The aqua line is the XRST signal

3） The purple line is the EMU0 signal

4） The green line is the EMU1 signal

8）Operation mode:

9）Results:

Experiment Number	Operation Mode entered	Signals Description	Program Run correctly	Else
1	Normal mode	Figure 1	Yes, led blinking
2	Wait in reset mode	Figure 2	No
3	Reserved for testing	Figure 3	No
4	Slave mode	Figure 4	Yes, led blinking

10）Figures:

【Figure 1】 Experiment 1, Power on moment（Normal Mode entered）

【Figure 2】 Experiment 2, Power on moment（Wait in reset mode entered）

【Figure 3】 Experiment 4, Power on moment（Reserved for testing mode entered）

【Figure 4】 Experiment 6, Power on moment（Slave mode entered）

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Operation Mode Control--Jones Chen